Honestly I feel like the two assassins who’d be unlikely best friends are Connor Kenway/Ratonhnhaké:ton and Jacob Frye, their personalities are complete opposites and that makes it even BETTER!
You can love a character and still admit when they’re wrong. I love Jacob but i can acknowledge his flaws (he has none) & can hold him accountable for his wrongdoings (he’s never done anything wrong in his life) & call him out for her actions (which are always correct).