Brutest achievement quick answer
Brutest requires 50,000 total damage in one eligible run, not a single 50,000-damage hit. Check the Codex mode requirement before starting.
In the linked discussion, Path_of_Circles suggests Body Slam or Trunk with Size and attack-area increases, plus the boss evolution they call Pollination to visit more points of interest and spawn enemies. The420elephant adds Social abilities to pull enemies closer. These are player suggestions, not a verified success rate.
Another commenter, abstractadvocat, proposes Chonky, More Mass, Muscular Tissue, Jaws/Stalker, Nocturnal, Ambush, Minimalist and Underdog for a large hit after leaving Burrow at night. That comment describes a single-hit combination; it does not report a completed 50,000-total-damage run.
In an October 2 reply to a player who was 10,000 damage short, abstractadvocat suggested a Physical route: splice Underdog with Spawn of Chaos, reroll the latter for a strong Physical start, then stack Chonky, More Mass and Muscular Tissue before adding Arms, Nocturnal, Jaws and an Ambush exit from Burrow. This is a route suggestion, not a documented Brutest unlock; verify the current card values in-game.
Related guides: Chonk Body Slam, Physical Predator, Cataclysm Final Boss.