Superior Firepower Achievement
Complete all levels on 'Ultra-Violence' or higher in Single player
For this one, you have to finish every single level on “Ultra-Violence.” The best way to go about doing this is to take each level slow and steady. Save very often, since you are allowed to save anywhere, so make good use of that. Be careful not to save while moving, you may load and be falling into a pit with no escape. Conserve all the ammo you can, chainsaw pink demons instead of use ammo. Doom II is about the same as the first one. There are a lot less hard levels in this game though.
NOTE: Secret levels are NOT required.