Uncanny X-Men No. 137: Truly a seminal comic in the history of the genre. Dark Phoenix, once Jean Grey, sacrifices herself to save the universe after destroying an entire galaxy while possessed by the Phoenix force. Chris Claremont and John Byrne at the height of their powers created a book that is still beautiful to both look at and to read. It seemed Jean was really going to stay dead until the mid-80s when she was brought back as part of an Avengers storyline. After that, Jean Grey was killed and brought back to life seemingly on an annual basis. But this issue was and continues to be one that stands out more than three decades later.