Shadow was conceptualized as Sonic's Vegeta but he's not at all like Vegeta, who's more of just a cocky asshole piece of shit with a no-nonsense attitude (with the "muh pride" aspect of his personality turned up to eleven when he knocked Bulma up). Shadow's always been more of a traditional dark brooding manga anti-hero with a tragic past, the kind of character who's always on a mission and ends up collaborating with the MC out of self-reflecting on his backstory.