Malice
What is this thing? The entity known as Malice has possessed the bodies of Alison Blaire (the Dazzler), Wolverine, Rogue, Ororo (Storm), Lorna Dane (Polaris), Beatrice Conners, Alex Summers (Havok), and Sue Richards (the Invisible Woman). The Sue Richards' version of Malice appears to be a psychological manifestation of Sue's own dark side left over from the Infinity Wars; in any case, it is not the mutant of the same name that dogs the X-Folks.
First appearance: Well, something named Malice showed up in Jungle Action 8.
Died in: The mutant Malice was caught with no where to go in X-Factor 105. The alternate personality Malice...well, those alternate personalities never really die, do they?
Team affiliation: When in league with Mister Sinister, Malice was partial to Polaris of X-Factor (Uncanny X-Men 221-222) although left on her own she tried to destroy Polaris rather than be permanently tied to her (X-Factor 102-105). Malice was the field leader for Sinister's Marauders during the Mutant Massacre. The Invisible Woman attempted to integrate Malice into her own personality (Fantastic Four 368), which made her very cranky for a considerable period of time.
Powers: Malice is a strongly empathic entity with no known corporal form. She specializes in disrupting the emotional center of the brain, emphasizing the emotions at the expense of rational thought. (This, incidentally, works for both versions of Malice...)
Favorite quote, the mutant Malice: "Let's not do anything rash, shall we? Although I'm dying to see what a point-blank plasma blast to the temple would look like..." (Malice threatening to use the possessed Havok as a murder weapon, X-Factor 104).
Favorite quote, the alternate personality Malice: "Repression can be extremely hazardous to a delicate psyche -- but you've never been as delicate as you appear!" (Fantastic Four 365)
Favorite storyline: X-Factor 105, where Havok and Polaris each attempt self-sacrifice rather than let the other be possessed by Malice.
Least favorite storyline: Uncanny X-Men 219. Waaay too much body hopping in too short a time; it was very difficult to figure out what was happening to whom when.
Confession time: I don't have any of the Jungle Action books, so I have no idea if that Malice is related to either of the other Malices. Anybody else know?
Response to confession time: From Russ Chappell, who runs the Marvel Chronology Project: "Unrelated. The Jungle Action Malice was one of several hired guns sent by Eric Killmonger to bedevil the Black Panther. Among the others were Lord Karnaj (unrelated to the Spider-Man symbiote villain) and Venomm (unrelated to the Captain America/Spider-Man villain)."