WARNING: The following contains spoilers for Marauders #22, on sale now from Marvel Comics.
Emma Frost spent years as one of the X-Men's deadliest foes. A powerful and ruthless telepath, Emma served as the White Queen of the Hellfire Club and came up against the X-Men multiple times. She particularly gained the ire of Storm and Kitty Pryde while simultaneously discovering a passion for teaching, and taking on a class of mutant students. This began a long road towards Emma finding a redemption of sorts with her former enemies, throwing herself into guiding the next generation of mutants and becoming a hero, even when her pragmatic approach to the world could still paint her as a villain.
But even when she has good intentions, she's proven willing to work with villains -- such as when she became a part of Norman Osborn's Cabal of villains during Dark Reign. However, it turns out that there's another Spider-Man villain who Emma used to work with. As revealed in Marauders #22 by Gerry Duggan, Matteo Lolli, Klaus Janson, Rain Beredo & VC's Cory Petit, Emma once found herself tasked with helping Lourdes Chantel -- a fellow woman in the male-dominated Hellfire Club -- escape the reach of her abusive lover, Sebastian Shaw. To do so, she turned to Wilson Fisk, the Kingpin, for help.
Helping Chantel fake her death during a Sentinel attack (and changing the history of mutants forever by setting up Shaw to take control of the Hellfire Club in vengeance for her demise), Emma then revealed she had a "friend" she'd done business with in the past -- Wilson Fisk, aka the Kingpin. It turns out that during this time in her life, Emma Frost worked for Fisk, serving as his resident telepath. Due to some unrevealed debt, Emma agreed to a "contract" that saw her "fixing" the minds of people Fisk needed to be changed.
Although she clearly hates the arrangement -- and is forced to extend it for Kingpin to be willing to assist Chantel -- Emma agrees to it. In the present day, she describes the cost as "high," but eventually worked off the debt and refuses to talk about those days in any more detail. All of this goes to show that Emma Frost, even at the more villainous days of her life, was still driven by some amount of humanity. She willingly took on tasks she despised, all for the sake of helping another woman escape a terrible situation.
But it's also a reminder that Emma has connections throughout the villain community, and that gives her a certain edge the more noble defenders of Krakoa lack. When Emma is forced to make a hard decision that she believes is for the greater good, she has fewer moral complications than her fellow mutant heroes. Her deal with Kingpin -- a frequent foe of Spider-Man, Daredevil, and the Punisher -- may have genuinely affected any of their lives, and her impact might still be felt on that corner of the Marvel Universe.
Along with the revelation of Chantel's survival, this all suggests that Emma's more villainous days had a serious impact on the overall Marvel Universe, even if no one was fully aware of just how vital she really was. It's possible that Fisk may call upon that alliance again some day, giving the criminal Kingpin a potential in with a major power-player in the Quiet Council and one of the heads of the Hellfire Trading Corporation.