Metal Sonic

Heartless, cold, killing machine (literally). In my opinion, this is the ultimate viliian in the Sonic universe and is overlooked far too often by SEGA. Instead of coming up with new useless hedgehogs, *cough*silver*cough*, they should simply recycle Metal from time-to-time.
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After spending about 30 minutes trying to find two others, I can't seem to settle on just two more. Metal Sonic is the most obvious to me, but there always seems to be ties for 2nd and 3rd.