DOOM + DOOM II

Game: Legacy of Rust
Episode 2, Map 6: Soul Silo
Cheats Used: IDDQD, IDKFA, IDCLIP (no clip)
Achieved on: Xbox Series X. To input cheat codes I used an Xbox controller keyboard. (Has great functionality)

For this method. Start off by activating all cheats listed above. Bring out the Calamity Blade weapon. (The silver crossbow looking weapon) Then make your way over to the spot shown on the in game minimap (white dot is you). Once here turn noclip back off to make the trigger work. Once turned off make you're way forward running over either the left or right fuel tank pickups which is on the way to the pits filled with Imps. This will trigger BOTH pits to raise up, and TONS of easy imps coming at you. Making for an breezy achievement.

Legacy of Rust Episode 2 mission 6 Soul Silo on the left hand side of the map if you no clip (IDCLIP) you will come across loads of acid and pits with basic imps in. I quick saved just outside the pit then pre charged that crappy weapon. As I went into the pit it would go off, if I didn’t get the achievement I would just quick load and try again. I did have it on nightmare and respawning enemies to give myself a chance.

Added image link so you get a rough idea where to try it.

https://imgur.com/a/hVNGYGT

For those who don't have a keyboard and are on Xbox.

Level select: E2M6: Soul Silo
Difficulty : I'm Too Young To Die

Proceed through the level until you reach the yellow keycard. As you go to pick it up you'll be teleported into a toxic filled room with a BFG in-front of you and two fuel ammos to the left and right on small walkways.

Switch to the Calamity Blade and walk towards one of the two fuel ammos. As you reach the ammo a lift full of imps will start to rise up. Charge up the blade and release it as the imps reach the top.

Legacy of Rust Episode 2 mission 6 Soul Silo on the left hand side of the map if you no clip you will come across loads of acid and pits with basic imps in. I quick saved just outside the pit then pre charged that crappy weapon. As I went into the pit it would go off, if I didn’t get the achievement I would just quick load and try again. I did have it on nightmare and respawning enemies to give myself a chance.

Added image link so you get a rough idea where to try it.

https://imgur.com/a/hVNGYGT

Legacy of Rust, Episode 2: Counterfeit Eden, Mission 6: Soul Silo

Recommend I'm Too Young To Die Difficulty as it doesn't affect enemy spawn density in this level, just health.

Start the mission and, using a Keyboard, open the map and type IDDT twice to unveil the entirety of the map, including Enemies. Close the map and type IDDQD for God Mode, and IDFKA for all keys and guns.

Head out of spawn and turn left, go through the door past the Shotgunners, and follow the outdoor area around the curved pathway to the red key door.

Enter and hit the switch on the right side just inside the door to open the next door.

Go around to the right past the first column of Toxic Waste, then go left through the Blue Key door, next to the Incinerator weapon pickup on the floor. Follow this corridor all the way to the Yellow Key and go to pick it up.

You'll find you've been teleported to the area in the top left of the map (This is the final arena of the map leading to the end). Feel free to make a Quick Save.

Head forward and drop into the Pit. When you do, all of the Imps that are in the two adjacent pits to the east and west will be raised up to start attacking you.

Type in IDCLIP to enable Noclip and let yourself out of the pit by just walking into one of the walls, and find a spot with the Imps in front of you, where you have some space to be able to fire the Calamity Blade (Weapon 7) at full charge. You should be able to get well over 50 kills easily. If you run out of ammo just type IDFA or IDKFA again. Load your Quick Save if you end up killing too many, there's not much point in waiting for them to respawn with the modifier on.

Here is a quick map path I put together, follow the Cyan route. Starred locations are the Imp spawns.
https://imgur.com/a/JIrWbQ3