>>20492015>like literally anything elseTruant, Healer, Flower Veil, Big Pecks, etc, etc, etc.
Besides, both Insomnia and Steafast have use in Doubles, GF's "official" competitive format, and since a Legends competition was already done of course Mewtwo has found viability. Think of it: Y fucks up the usual Darkrai Dark Void setup, and with a bit of prediction, X can use a Fake Out user to its advantage.