To earn this achievement, "Are you A God", you need to beat professional difficulty, however, that is not as easy as it sounds.
First off, let me just say, that worrying about your health status is only important if you are alone without any other ghostbusters, or you are partnered up with Ray (Dan Ackroyd), as Ray's A.I. build is lazy.
Professional difficulty isn't that much more difficult than the Medium difficulty, but there are a few parts that may get you stuck.
The 3rd boss battle in the library fighting the collector can be a pain. My suggestions are as follows:
- When you first start the battle, switch to your Slime sprayer, and spray the collector's mask as normal.
- When Egon says "All Clear" Run back to where you originally started and switch to your Proton Pack. Pull of the collector's mask using the capture steam (LB).
- Now, start using the Blast power on the proton pack (LT) and fire on the collector's face. If he comes near you, jump in the portal on the left or right and you will be teleported to the other side of the map. STAY AS FAR AWAY AS POSSIBLE!
- Keep beaming him and venting your pack. If Egon or Ray fall, DO NOT REVIVE THEM. Luckily, the game does not force you to pick up your teammates, so just forget about them, and focus on the boss. I suggest this, because they'll only stand in one place and get knocked down again.
The 4th boss battle under the museum, facing the guy in the sewer like area can be difficult do to limited area of movement.
To easily beat this battle, when you first walk up to the platform where the battle starts, Destroy all the sides that can be destroyed to prevent the boss from taking cover.
Next, aim for the yellow ball on the bosses chest when he pops up, using the LT shooter on the new gun you received when you entered the basement. (It's the gun bound to Right on the D-Pad)
If the boss starts to throw blue like balls at you, STRAFE to the right, and you'll avoid them, this is extremely important as it causes instant death 90% of the time.
If your teammates fall down, revive them. When the pink portals open, close them using your slime gun. Then focus on the boss again.
The final thing that might make beating professional difficulty difficult, is the part in the cemetery level in which you must use your slime tether to slam flame stone angels into a gate wall....
My advice is to forget about using the slime tether, and use the proton capture steam (LB) and the slam ability (LT). Keep strafing in an oval shape in the middle of the area, facing the gate where the Ecto 1 is (The car). When Peter (Bill Murray) says: "12 O' Clock High" This means the angels have spawned, look up above the gate, and you should see them (They're on fire).
Grab one and slam it straight down into the gate. You need to do this 5 times total for the gate to break open. You will know you have 3 successful hits if Winston says "Its almost there".
If RAY falls, do not revive him, he's a waste of time, and 95% of the time you get to the "Revive" status, he doesn't pick you up.
Believe it or not, the last boss battle, is actually strangely easy on the hardest difficulty, just as long as you do not revive the other ghostbusters, and focus on the mayor by proton pack'ing him, and then using the ball rocket (LT) on the Proton Pack to destroy the green crystals when they reveal themselves.
Then when you have to fight the architect, just shoot him with the Mason gun (RIght on D-Pad), using the Right Trigger attack. Shoot three times, then vent, and repeat. When he enters the middle hole, he tries to recharge, just shoot the vase looking things to the north, south, east, and west, and he won't recharge, then repeat until his health is gone for the achievement!
So following those tips for those difficult parts, just play through the game as normal, and you should get this achievement pretty easily...