Well, I seemed to have missed the PE Proposal for this guy, but if it were still up, I'd have downvoted it. Doesn't help that the user who proposed him has proposed many failures who were obvious non-keepers.
Who is the character?
Metal Sonic is a major antagonist from the Sonic the Hedgehog IDW Comics series. He's a robotic copy of Sonic made by Eggman as an evil counterpart to him. He was temporarily the leader of the Eggman Empire.
Why he doesn't qualify
Ultimately, he doesn't do enough to count. Most of his villainy is quite generic, mostly being attempts to kill but having no actual bodycount or some other generic villainy. Not much he does is worse than the usual villain of his kind. He doesn't really come off as messed up like a PE villain usually would. And IDW Sonic does have a villain with a bodycount and he's not bad enough to be PE either, yet he still has some successful kills while Metal Sonic has none.
I find it worth noting that the original proposal doesn't actually say why he's worse than the usual Metal Sonic or why he's above the baseline in general (he really isn't above the baseline). The upvotes didn't really say how he's worse than a generic villain either.
Cut. I have no idea how he got approved to begin with.