Who has been Sonic's best rival so far?

[Neon The Hedgehog]

 

That said, I'd rather they focus on Metal because the dude seriously needs an actual character, and for it to be established as well.

             Yeah I wished that Metal sonic had some sort of personality too. I kind of grew to love that metal guy. I know Sonic 4 episode 2 had mixed reviews, but I had a lot of fun playing as Metal Sonic. It made me kind of want to get to know the character more. I get that he is a mindless robot, but it would kind of be cool if he had some sort of emotion anyway. I mean, Gamma got emotions even though he was a robot, so why not metal sonic as well?