2. Jean Grey
Thanks to both the Phoenix and the magic of comic book drama, it's hard to say what Jean has done and what she hasn't done, but one thing is for certain€”even if Jean Grey wasn't physically part of the Dark Phoenix Saga, she has enough layers to give her the Number Two spot on this list. Jean has been through a great deal in her time, from learning everything about Madelyne Pryor to all of those issues with kids from other timelines, but Jean Grey almost in fact transcends this list, because as she has put it, part of her has always been the Phoenix. She lives with more maturity and responsibility than most of the characters in the Marvel Universe, and with more memories churning within her than most people in any universe could bear. Through it all, she has always proven her mettle, again and again, from leading Xavier's School for Gifted Youngsters to standing up to Onslaught's temptations to even coming to the rescue of Emma Frost (several times). Her past self is even the leader of the past X-Men team in the present! And then there's her relationship with Scott, and all they've been through. Speaking of which...