The card we fear the most is Witchbane Orb, followed by Chalice of the Void
Getting this creature on the battlefield can swing games almost immediately, especially if you have a good creature base built up and some open targets to aim at
Its a shoo-in for decks like Oloro and Ayli and Karlov, all of which happen to be insanely popular EDH generals right now
4 Ajani, Adversary of Tyrants For white decks based around the use of creatures, Ajani, Adversary of Tyrants is a powerful four loyalty Planeswalker for four mana, capable of flexibly synergizing with creatures in several ways
Now, she won't toss on a bunch of +1 counters as easily, but neither of her first two abilities drain her, and her second is a strong one you can learn into
As such I mostly end up running these kinds of super to end when I don't have the required depth in cards