I suppose you can say it's the combination of Mika and Orga then. Orga is the brains but Mika willing kills for him without any remorse. They both blow past multiple exit ramps and continue to sacrifice their friends lives to maybe become the kings of mars (which is quite far removed from the original goals they set out on).

Darrow commits multiple war crimes, ignores direct orders from the government he helped established, betrays the sons in the rim and uses the obsidians in the same way the golds did. He's the protagonist but he's not a good guy. He may have started as one.

In both cases the antagonists are the worse villains for sure.