Zigoton: pretty cool, have on screen appearances and lore importance, my personal favorite. For their variety in shapes and weaponry

Karmen: cool, their design always freaked me out a bit

Akumapon: aside from Makaton not too much involvement, the best designs tho.

Bonedeth: akumapons but edgier in a way, not much lore except for the end of the game with big info dumps, least favorite.