The X-Men are certainly a tragic bunch (ex: everything), but perhaps none among them are quite so deeply maudlin as the Summers family. These folks have it all — lost children, orphan feelings, future kids, perfectionism, morally ambiguous father figures: every ingredient required for a deeply sad origin story.
This general sense of tragedy tends to blow up in their faces so regularly that it's more or less the ongoing B-plot (and often the A-, C-, and D-plots) of the story of the X-Men. For instance, there was that time that Jean Grey appeared to have died and Scott married an exact clone of her, named Madelyne Pryor, who ultimately became the Medea of the X-Men.
Madelyne Pryor & Scott Summers
When we first meet Madelyne, she's working as a cargo pilot, and her path crosses with Scott in Alaska, where his grandparents live. Minus the bangs, she is the exact spitting image of Jean Grey and the only surviving crew of a plane crash that had happened on the day of the Phoenix's apparent death. Professor X fails to get a psychic read on her, which isn't a complete aberration but does cause some concern. Despite these red flags, Scott is searching for an identity outside of the X-Men, and Madelyne is more than ready to start a family with him. They are married, and according to the original intentions of the story, that would be the last time we would see Cyclops on active team duty.
Anyone who has seen Cyclops gracing the cover of hundreds of X-Men comics over the last few decades would be aware that this isn't exactly how that all panned out. Though they had a period of relative happiness, they were also almost immediately carried away into Asgardian drama with the rest of the X-Men, where the apparently human Madelyne became the mystical hero Anodyne before ultimately forsaking these Loki-granted powers. It is at the end of this story that we discover that Madelyne is pregnant, which entails a joyous celebration that unfortunately is doomed to end in tragedy and horror because ... well, it's an X-Men story.
Ultimately, Madelyne gives birth alone in the X-Mansion, which is possibly one of the most ironic moments of her life to that point (more on the way, though). When she attempts to confront Scott about leaving her alone, he tries to guilt her by leveraging her duties as a mother. Storm interrupts the argument, sensing that Scott needs a wake-up call. She challenges him to a duel for leadership — which, even without the use of her powers, she wins.
Theoretically, this would force Scott to retire from the team, but even in Alaska with Maddie and his child (Nathan, who would eventually become Cable), he is still haunted by Jean and the X-Men, and he is distant to Madelyne in a way that she is absolutely not prepared to deal with. Scott receives a phone call one day in which Angel informs him that Jean has been found alive, and, with no explanation, Scott leaves Madelyne and his son forever.
The Goblin Queen
In the wake of Scott's abandonment, Madelyne and their son are attacked by the Marauders, who kidnap the child and leave her for dead. She survives but suffers from suicidal depression. The X-Men come for her in her hour of need, but Cyclops is no longer among them, having gone off to form X-Factor with the rest of the original X-Men. Madelyne and Scott's brother Alex form a closer bond, which ultimately becomes romantic as she helps the team with her technical mastery.
Everything might have worked out, but after Madelyne realized that Scott and Jean had reunited, a demon known as S'ym from the Limbo dimension enters her dreaming mind and tempts her with ultimate power. Later, when men in Genosha attempt to subjugate Madelyne, powers surprisingly emerge, and she kills them all in a moment. She begins negotiating for power in Limbo as the Goblin Queen.
The villain Mister Sinister eventually informs Madelyne of her true origins, wherein he cloned her from Jean Grey specifically to love and be loved by Scott Summers. The knowledge that she is more or less nothing but a toy created by and for a man who no longer has any use for her drives Madelyne to rage, and she attempts to sacrifice her child. The conflicted Jean Grey chooses to merge with Phoenix and Madelyne, thus binding their consciousnesses, and Madelyne thereby dies in a sense but continues on in Jean's mind.
After Inferno, Madelyne's appearances became much more scattered. She saw a return in the Age of Apocalypse spin-off X-Man, where things got even weirder than ever before. Essentially, Nate Grey pulls her together out of memories and gives her sentient form, which is why we meet her as an amnesiac. Though Madelyne is essentially his mother from another reality, he begins a bizarre romantic relationship with her before she ultimately leaves with the villain Selene. She later claims to be a Jean Grey from an alternate reality, but it's hard to get into that without getting a continuity headache from all the loose plot threads the story presents.
She returns again as the Red Queen, existing in incorporeal form and still obsessed with Scott Summers. She attempts to bring herself back to life but fails. Disturbingly, in Avengers vs. X-Men, six Madelyne clones were created without individual personalities and were quickly destroyed by the Phoenix Force. She was also resurrected in a very complicated way by Amora as a part of Lady Deathstrike's Sisterhood, but that didn't go anywhere.
Perhaps the best story arc for Madelyne post-Inferno was the Mutant X alternate reality, in which she is married to Havok and serves as one of the major heroes of that reality. Her mind is overtaken by the Goblin Queen, which becomes a separate entity. This removal of her autonomy is not great, but the fact is that the series still gave us a complicated and believable Maddie.
As we speak, Madelyne is seeing her return to the X-books. Revealed briefly in Sinister's notes as being not only still alive but still very packed with story potential, Madelyne will hopefully see a better, more interesting future. Her original arc in Inferno is one of the best X-Men villain-to-hero stories ever told, and subsequent stories where her character is used for shock value and story convenience without any payoff have been disappointing.
Much like Jean Grey, the woman she was made from, Madelyne's story becomes one about autonomy via the removal of it. She was created as a cipher, and the love of her life left her completely vulnerable to attacks from his rogues' gallery. Her actions always seemed at least justified, though no less harmful as a result. Questions of identity and free will loom large in Madelyne's story, which is why it would be a damn shame to see her potential as a complicated villain wasted once more on another meaningless resurrection.