DOOM

I got this in the "Easy SnapPoints v2.0" SnapMap. It is currently on all featured playlists, and can be searched for as well. It is basically you with a BFG melting elite demons. Took me about 5 minutes, summoning the waves with your fourth taunt (left on the D-pad).

I have created a SnapMap as a one-stop shop for several achievements, including this one. To find it, simply hit to open the search function from any tab in the SnapMap mode and search for "KFADVXWV" (the capitalization does not matter.) Once you locate the map, make sure you hit to "Play" the map, because "Save to my downloaded maps" will not count if you launch it from your downloaded maps.

Setting the lobby type to private does not void this achievement.

If you follow the short tutorial texts on the screen, you can continue into a small arena and use buttons on your controller to spawn demons. You are (nearly) invincible, have infinite ammo, and permanent quad damage once you enter the arena part of the map.

For this achievement, simply hit and/or to spawn enemies and melt them with the BFG. Because you have permanent quad damage, every kill you get counts as a powerup kill while in the arena. You can hit the spawner buttons as many times as you like, but the game will only allow 12 demons on the screen at any one time.

This map is also great for:

Solution for Timing is Everything In DOOM
Solution for Up Close and Personal In DOOM
Solution for No Rest for the Living In DOOM
Solution for Butcher In DOOM

During the story mode when you come across a Gore Nest normally there are Power Ups near by. Find the Power Up then destroy the Gore Nest which will spawn all the enemies. Grab the power up and start killing the enemies but DO NOT KILL THEM ALL. If you kill them all you will get a checkpoint. Instead when there is one or two left, just hit the start button and restart from last checkpoint and all your kills will count towards the achievement and the Gore Nest and Power Up will be back. Just rinse and repeat until you get to 150 kills.

Similar solution to the other guys before. One that I found while I was halfway through the achievement was a SnapMap. It is called Devil City Ransom. There are two power-ups in the beginning of the 2nd and 3rd sections of the map. Pretty fun map too. I restarted the map 3 times and I got the achievement.