9. Cyclops And Emma Frost's Psychic Affair
Scott Summers is known for his by-the-book attitude, but throughout his career as Cyclops he has done morally questionable things such as leaving his wife Jean Grey and their child. But during a troubled time in their marriage, Slim would cheat on Jean in Grant Morrison's New X-Men.
This begins when a rift between the two is caused by Scott's recent encounter with Apocalypse while the Phoenix Force manifests through Jean once again. This leads to the couple confiding in other people, with Grey kissing Wolverine, while Summers vents out to Emma Frost in a series of psychic therapy sessions. Eventually, however, Scott and Emma's relationship becomes intimate and they have a psychic affair. The pair are soon caught by Jean and, in the aftermath, Cyclops leaves the team while Emma is believed to have been killed. The whole thing even gets messier when Jean dies but convinces a grieving Scott to move on - which he does by kissing Ms. Frost beside his wife's grave.
Though Cyclops would defend himself by saying that it was only thoughts and no physical contact was made, his infamous affair would remain a dent in his character.