Stack
Might before approaching the four
K1T-A golems, pull them together to kill them so that the Chaos Anomaly spawns.
Alternatively, you can check if you still need one of them for the Kitty Compactor and focus on it. Every 25% health, The Chaos Anomaly will become immune to damage and you have to kill K1T-A golems again to continue. With every phase there will be one less K1T-A golem but the remaining grow in strength. The final single golem at 25% health has about 1.5m health and is a champion.
This is the one that will count towards the achievement. The last golem to be killed is the one that will not spawn in the next phase.
Pay attention to the
Knockback zones from the small JT-12 golems and look out for
Flux Bombs, the debuff can be hard to notice on the mosaic ground.