Sonic the Hedgehog has faced a countless number of adversaries since he first popped up in 1991. Some of his most iconic rivals include Metal Sonic from 1993s Sonic CD, Silver the Hedgehog from Sonic The Hedgehog 2006, and of course, Knuckles the Echidna from 1994s Sonic The Hedgehog 3. The blue blur has tussled with many foes, but almost always manages to come out on top. But out of all of these enemies, the one that Sonic is most often compared to is Shadow The Hedgehog, the ultimate life form.