The hardest ODST par score achievement, no doubt. I had to try A LOT of different combinations between difficulties and skulls to pull this off solo. In the process, I got very good on this level. I must have played it about 25 times, no less. You don't have to do this though, for I will tell you the ideal combination if like me you plan to do this by yourself alone.
My final score was 133,398, so way over the 90k asked, but my previous attempts although got higher and higher each time, the closest one had been 83k. The multipliers are part of the key to get this done properly.
My final time was 24:04 (anything below 25 earns a gorgeous and needed times three (3x) multiplier. We need that, we want that.
Then I used the 7 skulls that I personally hate less and that after so much trial and error I found that were the ones that wouldn't get in the way. From the skulls I got a final 2.06x multiplier.
Legendary is full of bullshit. Stupid things happen more often, Buck gets dumber... you name it. Heroic is a little less infuriating and gives you a 2x multiplier. When I noticed that time would be an essential part in this, I was divided between Heroic or Normal. The problem with Normal is that although the enemies die faster, there's no bonus multiplier. I've finished some really good runs playing on Normal, but eventually when I got this I was playing on Heroic.
Now, about the skulls:
- Black Eye (DO NOT use it). Reason: you will take a lot of damage throughout this mission. You cannot risk having to punch someone to have shields back up while also focusing in so many other things. Besides, who are you gonna punch when fighting Banshees and Ghosts?
- Blind (Optional). On a few of my runs I had Blind on. I also had a sticky on my TV screen so I wouldn't loose the aim. But still, somehow it's awkward to play without the HUD elements. I needed to know how much ammo I had to plan when to use it in the last firefight, so on my final run I gave up on Blind and its meager 1.10x multiplier.
- Catch (better not to use). Just like Blind, I gave it a few tries and it worked a few times, less often than I needed though. Even without this skull enemies will try to stick grenade you if they catch you off guard. With the skull the chances of this happening just increase a lot and can ruin a good run. You don't want to risk it, do you?
- Famine (ON): While I would like to have more Plasma Cannon and Plasma Pistol ammo, it's totally possible to go without them.
- Iron (ON): playing solo this is a must in my opinion. It has the best multiplier than any of the other skulls and you can save and quit as soon as you die if BS happens.
- Mythic, Thunderstorm and Tilt (DO NOT use them, although I had thunderstorm on my last run). I'm not sure about the specifics of each of these skulls in terms of math and mechanics, but it is best to avoid them because to be fast you want to kill the enemies in 2 or 3 shots max. I thought Tilt was the less harmful one among them, but when it says that it increases enemies resistances it is not kidding. Enemy vehicles taking 4 or more shots to go down is no good.
- Tough Luck (ON): I don't mind having Brutes going berserk and enemies fleeing less often. In fact, I wanted that so I could headshot the first and run over the last.
Important: try to avoid saving and quitting at the final firefight part. Your time and your score might not be registered if you do that. Also, it seems that after saving and quitting, when you resume your time is that of just before quitting instead of your last good checkpoint. So it's not good to do that a lot. On my final run I only died 2 times. I was amazed that I still was able to finish below par time. Ideally you don't want to die so you don't loose time at all.
Now I'll tell you exactly what my strategy was all the way.
From start push forward even before the level starts and once out of the building proceed left towards the area where the enemies are. Keep hugging the wall and go underneath the building. Avoid the enemies at first (do not start shooting here), past the Brutes and Jackals and go where the Rocket Launcher is on the left. As soon as you have it destroy the tower in the middle for a triple kill (aim below one of the turrets, because sometimes it won't give you any medals if you aim at the tower). Now you can time and waste your rockets towards where all of the enemies are. You should get a couple of multi kills in the process. Once you are done (Buck will say "That's the last of them!") run towards the building where the elevator is and as soon as you pass through the door (you have to, so Buck and Dare will activate their speech and proceed), wait for Virgil with the door open, but don't stand on its way. You want to wait until Virgil gets inside, then once it is on the dark hallway come behind him and start pushing it towards the door it has to open so it will get there faster. Once it starts to work on openning it, stay beside it and be ready to activate the door. If everything is done in good pace here, you should finish this beginning in no more than 3 or 3:30 minutes.
Skip the next cutscene and immediately push left. Get on the Warthog and drive Buck, who will be your turret man. Get speed and run over Grunts while he shoots them. Drive back and forth to kill as many little guys as possible. Be careful with sticky grenades, always keep a safe distance when driving and whenever you need to turn. Keep driving and running over guys. Be mindful of one Grunt with a Plasma Cannon on the right side of the road. After he's dead, grab his gun. Before moving through the next door, there's also a Rocket Launcher laying in the middle of the road by the door with a dead trooper and 2 medkits. Grab the weapon.
The next section is similar to the first one: drive back and forward running over enemies (this time a lot of Jackals at first) while Buck guns them with the turret. Pay attention when closer to the door for the next session though. You can run over the Brutes just like anybody else, whoever 90% of the time one of them will start throwing a grenade when you are about to run them, making the grenade stick to the car and blowing you up. This is very frustrating and a work around would be to have Buck gunning them or paying close attention and stopping the Warthog if they threaten to throw a grenade.
For the next section there will be 4 towers on the road, 2 of which will randomly spawn Grunts will Plasma Cannons. By now you should have a Rocket Launcher and a Plasma Cannon yourself. Do not get too close or Buck will start shooting at the tower, alerting the enemies. Check in which of the two first towers they are and aim a rocket at it. Once they blow up, move close to the tower's wreckage and savage 2 or 3 Plasma Cannons for extra ammo that should be on the floor. Don't move on foot or you will spend a lot of time going there and then back to the vehicle. After that, keep going forward to catch up to Dare and see if you can spot which of the final 2 towers have more little guys. Repeat the process and savage the ammo if you want. Now, this is important. Stop the Warthog not much further than the big truck that is on the middle of the road. In other words, do not go too close to the door. You have to keep some distance, not too far that you can't properly hit the enemies, nor too close that they will swarm at you. If you are in the right distance, eventually they will start coming at you, but not all at once. By the way, you won't let Buck on the turret here. Get him out, use this moment to swap guns with him and give him the Plasma Cannon (that is also important). He will move to "ride shotgun" (passenger's seat). After you kill all of the flying bugs start driving again (there's more Rocket ammo on a stand close by, but I never bothered to pick this one up though).
This next section is easy and more of the same. Two Phantoms will come and drop more Grunts, a few Jackals and Brutes. Run them over safely while Buck Plasma Cannon them.
The next part is the beginning of the pain. You have to protect Dare against lots of Ghosts but without drawing too much attention to you so they won't overwhelm you. When we gave Buck the Plasma Cannon, it was actually thinking about this next segment. It will be A LOT better having him shoot 4 green rockets in a row every few seconds than being on a regular turret. What I usually did was to advance little by little using Dare's truck as cover as well as the bumps in the middle of the road and tried to take on one enemy at a time. Eventually if I got in trouble with too many of them (it happened often) I rushed forward all the way to the door, parked the car with Buck's side facing the enemies and got out if we were still being shot (stay in the car if not, because you want the points for Buck's kills, which only happens if you are both on the same vehicle). As soon as the door opened, I ran towards the medkits on the left and got on the Gauss turret (ignored Bucks speech for a moment). Once the enemies stopped coming I would get Buck out of the first vehicle and them I sat on the passenger's seat of the Gauss Warthog. That will cause Buck to assume the Gauss, which he normally doesn't do if he has the Rocket Launcher or the Plasma Cannon. Another tatic for moving Buck to assume the Gauss is to take back the Plasma Cannon from him. We need Buck on the Gauss for the next part - and fast!
On this next part you want to drive a bit slow so it will help Buck to get shots in a row against the Banshees and the Ghosts. As long as you're not too far away and Dare is not being swarmed by enemies to the point of dying, you're doing it right. This is the second hardest part, just one more to go. Try to make sure that all the enemies are dead or at least far away and not pursuing you anymore before moving to the next segment.
This next part is the last hell section. Good things is that you only have Banshees to worry about. Forget about the Wraith for now, for some reason Buck isn't programmed to shoot straight at it even if you guys are face to face to it. He will shoot the sides of the Wraith and eventually kill the driver, but not the Wraith itself. Now, if you have played other levels and know that actually destroying vehicles (even spare ones) nets you a lot of points, that's what you know that you want to do. So, if Buck won't do it, don't waste your time. Have him take care of the Banshees as safely as possible and then once the next door opens get it, forget Buck from now on (yay!) and get into the Scorpion. Now you can go back and destroy that Wraith properly. Don't worry, you have the time if you already took care of all of the Banshees.
The following segment is easier as you will only have 2 turrets on the middle of the road to destroy, 4 Banshees and 1 orange Wraith that launches missiles (sorry, don't know the name yet). Let Dare go ahead in front of the Scorpion to draw the attention of the Wraith (go through the left if you want) and destroy it. I usually change lanes here, go to the right then stop and start picking the Banshees one by one. Don't forget to destroy the second turret from a distance if Dare is taking too much damage. Catch up with her afterwards.
On this next section you can destroy the 4 Phantoms that will fly you by on the left if you are fast enough. Each of them nets you a lot of points and I used to even reload the checkpoint in case I wasn't able to blow all of them up. Fortunately that is not necessary nor the most important thing. On my last run I think I was able to destroyed only one of them before moving on. Depending how good or bad you do here, you will have more enemies on the next part, which is sort of a compensation for the Phantoms you couldn't kill. As I was writting this I did a test and didn't shoot any of the Phantoms and then moved on. About 8 Ghosts and the same 2 turrets waited me on the other side of the door.
After that you will have your last encounter with enemies while drying the Scorpion Tank. They are all on foot and it's a nice last chance to get Killionary medals. I did real poorly on my run that unlocked the achievement getting only double and triple kills as I did poorly in other parts of that run but still was able to unlock it. That makes me think that the most important thing besides doing the best you can to kill as many enemies as possible and not get killed comes down to one other thing: time.
Behind the second to last there are no enemies. You will watch the giant Scarab making its way through the city and it will even shoot Dare at the end but it's all rehearsed. After the last door just move inside the middle tunnel and rush to kill the two sleeping grunts by the building your going to deffend. For this part I gave Buck the Plasma Cannon back (the Rocket Launcher will work too). You will loose some points as he kills enemies but at least he will help you to kill them faster if he has a good gun. There's more Rocket ammo inside the building to the right for you (not for Buck since his is infinite).
At the beginning of each wave I liked to be at the top right (facing the highway) turret. I only got unlucky 1 time by the last wave's Wraith shots and when that happened I was on the left one. Besides that I only left the turrets if enemies came too close and started throwing grenades or if a Brute with a Plasma Cannon or if a Hunter shot at me. Try to preserve those turrets. If your health is low, there are plenty of medkits behind you and inside on the bottom floor.
In the first wave I tried to target only the Grunts, as many as I could since they take less shots. Once they were taken care of and if no other enemy was at range of the turret I went down to assassinate, rocket or stick grenades at. Second wave is pretty much the same, I targeted as many Jackals without a shield as I could. Sometimes I killed them all, but on my last run I wasn't fast enough, so a few of them climbed the parking lot and started sniping me from there. Fortunately you have 2 Sniper Rifles on the top by the turrets, so it was easy and fast to dispach them. Buck killed the 2 Hunters more often that I did. On the last wave, I would see how many rockets I had left and use them wisely. After you kill all the Brutes, the one with the hammer will come for you, so I took back the gun I had given to Buck and rocket that last guy. Do not waste ammo when he is glowing. His overshield will run out in time. Just dodge and stay out of his reach.
This turned out to be a long solution, but I tried my best to describe it very well. If it ends up helping you in any way, you're welcome to leave a comment and a thumbs up to let me know. Thanks!