I mean they seem good enough friends from what I saw in the first movie, backing each other up with like the only real moment of actual physical aggression from robotnik being the time he woke up after he got fucking verbally owned at his own game and then knocked out by the cop he assumed was just a local hillbilly. Carrey-ass screaming about how much he loves the way Stone makes coffee, asking Stone to pin himself to the wall sohe can do his aggressive monologue, the small things like that kinda frame good reasons why he wouldn't just make Stone into a robot slave. He's not quite Jack Nicoloson's Joker's level of evil where he was already a seasoned criminal with a wacky sense of humor to the point he'll off his number one guy over some shit going wrong in his plans, at least not yet.