S.T.A.L.K.E.R. 2: Heart of Chornobyl

This can be done at practically any point in the game in a variety of locations but it's alwo one of the earlier achievements that you can get.

During the second main mission A Tough Awakening you'll be tasked with reaching the village of Zalissya, along the way you'll come along a group of bandits attacking aN NPC at a location marked on the map as Post Office. This NPC will give you the side mission Dangerous Visitors which requires you to reach the Boiler House and rescue Gloomy. Just outside the building you find Gloomy in as a cave with a series of anomalies and an artifact, if you pass right through this cave you should come across a group of allied NPC's fighting a couple of mutants.

Quick save before leaving the cave, aggro one of the mutants and then kite it back into the cave where you should have no problem baiting it into an anomaly. If you don't manage to pull it off just reload your save and try again.

This tends to be easy to do if you keep in mind where some anomalies are located like whirligigs. If you happen to be near one when a mutant tries to attack you you can lead them into it.

Mainly I just want to point out one anomaly in particular that I've enjoyed using for killing mutants. After leaving the Lesser Zone into Garbage you'll come across the anomaly that looks like tiny razor sharp glass shards. They can be tricky to see but they will sparkle a bit and you can often hear them pretty easily. What's nice about them is as long as you crouch walk through them you'll be fine. They make perfect traps since they don't need to be reset and mutants won't notice them and immediately kill themselves in it. Another great thing I noticed is they absorb bullets and even grenades. I tried it with a merc who had an SVD and he was unable to hurt me at all. Just waited at the edge until he had to reload and then killed him after stepping out of it. Could probably be handy if you get attacked by a group and happen to be near one. Still would be mindful of grenades since they could probably hurt you if they land near the anomaly and don't get absorbed into it.