Over the course of their journey, they have uncovered the threat of the Dark ... Titan, Thanos, as well as the latter's own ascension to the leader of the entire Galactic Council. Phoenix #8 ...

"The Dark Phoenix Saga" storyline spans Uncanny X-Men ... Doom, Galactus, and defeated Thanos. All of these characters have beaten Phoenix before, and Squirrel Girl beat all of them.