Chucillo. Mainly because according to my thinking, I thought any character played by Danny Trejo in a Robert Rodriguez flick should at least get killed onscreen, instead just being abducted offscreen, and given a mercy killing in the same manner. If a sequel is greenlit to PREDATORS, I hope Trejo is brought back for it in another role like he was in the El Mariachi films, and the two direct to video From Dusk Til Dawn sequels. Although, I'd have a feeling, even brought back as a new character, his death would go the same way. He'd basically be the "Kenny" of the PREDATORS franchise.
Nikoli. He went out herorically. Doing the right thing. But unfortunately ,unknown to him, the guy he saved was serial murder, and on top of it. Used Nik's kids as a ploy to get sympathy from Royce and Anna.