Metal knuckles, metal tails, and metal Amy did exist but they were destroyed in the comics. Though metal knuckles is a canon boss fight but labeled as Mecha knuckles. And metal knuckles was in sonic R so really metal sonic and metal knuckles are the only canon ones
MechaGodzilla DID YOU EVEN WATCH GODZILLA VS KONG? MECHAGODZILLA ALMOST DESTROYED GODZILLA and then kong came with the axe and godzilla and Kong team up to destroy mecha.