Featuring the following heroine!

Madame Masque

Real name: Whitney Frost

AKA: Countess Giuietta Nefaria. Big M. Krissy Longfellow

First appearance: Tales of Suspense 97.

Apparently assassinated in: Iron Man 238, by the woman who became the second Madame Masque. As near as I can tell, no one ever noticed the switch. Which made it pretty pointless, didn't it?

Team affiliation: Madame Masque was the head of the Maggia, and worked for Stark Enterprises in her Krissy Longfellow identity. Lately, the other Madame Masque has been hanging around Avengers Mansion, getting on the Black Widow's nerves.
Powers: Handy with guns. And something about that mask makes otherwise self-respecting superheros and S.H.E.I.L.D. agents behave like morons...
Favorite quote: "You're so cute when you try to be stealthy, dear." (To Bethany Cabe in Iron Man 139. A cat fight with semi-automatics followed!)

Favorite storyline: Iron Man 138-139, where she regained top form as the cold-blooded Maggia leader she was meant to be.

Least favorite storyline: Iron Man 91-116. Madame Masque stood around a lot and did nothing until the very end, where she abruptly turned against Iron Man at the urging of her father, Count Nefaria. In these issues, Whitney was utterly weak-willed. She couldn't even betray Tony Stark completely, standing by passively when the brief case containing Iron Man's armor fell into his hands. Unbelievable behavior for someone who headed up an international crime cartel.