I'm sorry, so very sorry, to be raising this question, but lately, it's been popping into my head and, as usual, I'm hoping to exorcise it by naming it, or at least asking the question.
I think I read it in early college, so around 2000, online, in English, maybe on a fanfic site. It was a fairly decent length, maybe 50-60 pages, and the scenes were fairly varied. The basic concept is pretty much exactly as noted above. The protagonist is a young male (teenager to young adult) who apparently has the mutant power to mind control others, and he decides to use it to sleep with all of the female Marvel heroines one by one. I think there was some conceit going on where he gained more power the more of them he was able to control/convert into his slaves. The only one that has stuck with me was Psylocke, who invoked some sort of "secret Asian sex technique" that involves him managing to ejaculate and urinate at the same time. Said technique had "gold" or "golden" in it. I think that part of his taking over Sue Storm involved setting Malice free complete with the choker appearing (which yes, mixes two of the villains named Malice). I think there may have been some bit where he also gained control over Mr. Fantastic and there was a joke about "being able to stretch any part of his body" in a stereotypical sex manner.
The only other detail that I remember clearly is that it later turns out that the protagonist's mentally disabled (maybe only seemingly, because the power kept her from focusing?) sister was the one with the mind control power. I vaguely remember that there was a scene (flashback?) halfway or two-thirds through the story where she was in a towel and it fell off, and I think that either precipitated the protagonist's mind control, or revealed to him that she was the one with the power all along.