Which card, in your opinion, was the zero-to-hero of Space-Time Smackdown?

So, the set's been out for three weeks now, and the meta seems to be settling. The contents of the set were leaked a few days before release, and people were making preliminary calls on what would be broken, and what would be useless. Pretty much everybody predicted that Darkrai EX would be pwerful, and correctly so, but there were some cards that were written off early on, only for them to rise to the top as players realise how good they can be with the right partners.

Which is why I decided to post this discussion topic: which card in Space-Time Smackdown got the biggest redemption arc? Which card was brushed off and deemed worthless at first, only to return with vengeance and make everyone sick of playing against it?