Sheamus isn't actually a bad vote for most improved. I at least see it having more merit than Zack Ryder who actually hasn't changed at all. Sheamus sorta had the R-Truth mode of improvement going-- changing gimmicks/alignments and working it well. Reason I think R-Truth is so much more deserving is he changed his character more and changed from borderline unwatchable to excellent whereas Sheamus was pretty decent as a heel too.
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I tried to have a fierce rivalry with SuperNiceDog, but he made me look worse than a GameFAQs Contest!