We'll be doing the same trick of using the cheats to cheese the entire Insane playthrough. It just takes a bit more menu-ing since the DLC is in its own tab, a bit further away from the cheats tab. Just like with the base game, all chapters can be completed using QCCs through chapter select - no need to carry weapons from another chapter forward into the next.
Chapter 01: Rude Awakening
There's absolutely nothing going on here, so you don't need to QCC at all. Just rush to the end (the passcode for the lift is 1503).
Chapter 02: Going Down
Walk along until you find the expander, then QCC, and come back. You'll get another checkpoint after defeating all the enemies, so that gives you a good place to come back with cheats off. Finish the level from here, since it's just a quick walk past some doors.
Chapter 03: In Security
You get a checkpoint when you enter the third bioscan. QCC here so you can just run through all of the lasers and do it again when you enter the ambush-y room. Quit and come back after getting to the computer room, but stay in a non-cheat state so you can finish the level like that. If you don't get credit for this the first time through, try quitting out by catching the chapter's last save before the fadeout.
Chapter 04: The Clone Carousel
QCC when the chapter loads since there are no checkpoints between the start and the battle in the first room. Quit out and come back cheat-less for the platforming part since you don't need cheats for it. Finish the chapter like this and quit out at the end for safety.
Chapter 05: Me, Myself and I
Distract some clones by setting up the film reel, then head up to the second floor and start QCCing when you feel like you have to. Quit out when you fall down in the vents that lead to the next chapter.
Chapter 06: Meat Grinder
This is just a platforming and driving chapter, so you don't need to deal with cheats for this one.
Chapter 07: The Doctor Is In
You should QCC for the first time when you enter Dr. Proton's arena so you can survive the big horde of exploding balls. Doing it a second time will help turn his fight into a joke. Since there's no checkpoint between killing Dr. Proton and loading the next chapter, you need to quit out when the last save is taking place when Dylan is rambling on to you.
Chapter 08: Magic Carpet Ride
Use QCC to get over the starting lasers if you want to be lazy. Otherwise, make your first QCC the first time aliens show up and keep it up until the platform reaches the end. Quit out during the last save.
Chapter 09: Drunken Crane Master
Use QCC for the first confrontation, then come back in a cheat-less state. You'll only encounter one more pigcop after doing the crane puzzle; using QCC again for that is up to you, though it might not be worth your time.
Chapter 10: All Your Base...
Use QCCs to get through the entire chapter. Since it's pretty straight-forward, it shouldn't take very long.
Chapter 11: Tunnel Vision
Use QCCs again, this time only up to where you reach the short bus. You can get through to the end after quitting out and becoming a non-cheating Duke.
Chapter 12: The Burning Bush
The last pacifist-ish chapter. Go outside and grab the gas by the tractor for the generator, and hide in the basement until you're normal size, then punch the pigcop about five times. Finally, punch out the two jerks harassing the girls and talk with Dr. Valencia again. Dylan is in the middle trailer behind the building.
Chapter 13: Teleportation Spire
Walk into the teleportation facility and grab a ripper for its faster fire rate. Use QCCs to get through all of the enemies. From personal experience, I managed to get credit for this chapter even though I didn't catch the last save before the next loading screen. If you're not so lucky, only use one QCC to get through the bigger wave of enemies, then quit and come back to take on the remaining bits the real way. That should stop any struggling the game has with your actions.
Chapter 14: Duke Side of the Moon
One last bit of QCC cheesing, and you should be totally done with this mess. Don't bother with QCCs until your rover breaks down since you aren't in a lot of danger until then. The cheats make you invincible, so getting the fuel rod should be easy as pie. Use a QCC at the start of the empress fight; your next checkpoint will occur after you take out one of the ovaries. You can QCC the second ovary as well - you get a checkpoint right before you have to drive the rover into the empress's face, so make sure you're in a not-cheating state for that. With that last push, you'll beat the boss.
It may have taken a lot of perseverance. It may have burned awful images into your memory for the rest of your life. You may have stopped playing this game for several years before deciding to come back to it. You may have had the absolute worst time of your life. But what matters here is that you've done it - you've conquered one of the worst games ever created. You have moved this task that belongs in "the future" and finished it, pushing it into "the past." Your future has gotten a lot brighter now that this horrible blemish has been vanquished.
Congratulate yourself, if you can. Take a break. Talk to people you love. Try to forget what you've seen. Have a nice meal. Get well soon.
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