While I dont tend to evaluate planeswalkers by their ultimate, Ugin, Eye of the Storms actually has one that is reasonable to get to
She can take all the investigator cards, giving her a lot of ability to make things dead, and a very small amount of ability to do much else beside spend AP inefficiently on healing
Although this is a great move in theory, there are some problems, first, if you have a full Bench, or at least not 3 open spots, the move's effectiveness is reduced, second, you need to have Fire type GX or EX cards in your deck to use this move, and third, if you have that many GX or EX cards in your discard pile, you're probably either about to lose the game, or you've already used a GX move and can't use this move
Fittingly, Imposter Syndrome is an impressive copy engine and token generator in the right deck
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