Marvel vs Sonic

Connection:

Both are antagonistic advanced robots who are created by one of the most brilliant scientists in (Ant-Man/ Hank Pym and Doctor Eggman respectively) in the hopes of reaching their goals (Hank modelled Ultron after his own mind to create an AI that can learn and adapt on its own, while Eggman made Metal to surpass and destroy his rival Sonic the Hedgehog)

Both have rebelled against their creators. The contrast is that Eggman is able to reign Metal in at times while Ultron is completely free from Hank's control and acts independently

Both also have numerous forms in which one is a giant (Ultron-7 and Metal Overlord respectively) and another is colored gold with magical or god-like powers (All-Father Ultron and Super Neo Metal Sonic)