I actually didn't make an entry because I didn't know how to make Gren villainous without seemingly too over the top. Since he already kinda has the "Token Evil Teammate" thing going on right now, he's just affable about his villainy. 

His villainous concept would have actually not really been evil, but more like "He's a villain because he is your enemy" sort of deal. That is to say, he stayed with the White Fang even after realizing their major faults, but instead of cutting ties he tries to stick with it and lead them in the right direction. A right, violent direction. He's also be less cheery and much more gruff. Tropes to describe him would have been "Knight in Sour Armor" and "Well-Intention Extremist", though I couldn't really muster up the number crunch for it. So sad.