DOOM + DOOM II

if you are doing this on Xbox you will need to plug in a keyboard to type in cheats

Boot up No Rest for the Living and start the first level on any difficulty (I left it on "Hurt Me Plenty") as we will be using the God Mode cheat

When you start type in the cheat "IDCLEV08" and it will start you in the last level

Type in "IDDQD" for God mode
Type in "IDCLIP" to be able to clip (walk) through walls

Directly infront of you will be a square platform that will be too high to get on if you arent using the NoClip cheat, simply walk into it and you will be ontop of a Pentagram, turn off NoClip by typing in "IDCLIP" and stay on the Pentagram, few seconds later you will finish the level and the achievement will be yours (you may have to move around slightly but try not to fall off)

Because you are typing in "IDCLIP" whenever you push the D button you will move to the right slightly, be careful not to fall off, best way is to stand on the left side of the platform so you dont fall when typing

Start a new game in No Rest

Type IDCLEV08

IDDQD god mode, IDKFA for full inventory, and IDCLIP so you can head straight ahead a short bit to a pillar/teleport that will end the level.

I have an easy method since you don't need to kill the Cyberdemon to finish the campaign. You can fully play this campaign with no enemies enabled. Simply take your time finishing, the achievement is yours.