>>712924137Shadow and Sonic really don't have much of a relationship or connection in Sonic Adventure 2, the story itself isn't really set up for them to become that kind of relationship in the future really.
They're on opposing sides and happen to meet incidentally three times in the story due to that reason, but that's the extent of their connection. They also have similar powers sure but neither of them care about something like that.
It's not like Vegeta and Goku who have the who same race thing going on, and class difference, and also actually beating the shit out of him, and caring about competing martial arts prowess.