Real Name: Unknown
Mutant Power: N/A; Madame Hydra is a regular human.
Voice Actor: Lisa Ann Beley
Guest Appearance: "Target X"
Back Story: Madame Hydra is the leader of HYDRA, the rogue organization that seems to be the "bad" version of S.H.I.E.L.D. Anything else about her past is unknown. During an attempt to recapture X23, plans went astray, and X23 ended up destroying the escape ship that Madame Hydra took off in. She's presumably dead at this time.
Personality: Madame Hydra had, like, 7 lines, so it's hard to glean a personality off of just that. As far as I can tell, though, she's your typical "evil Russian female operative" stereotype, nothing more.
Final Reflections: Madame Hydra was a very stereotypical villain, so she never really attracted my attention during the few moments she actually was on screen during the series. And now she's dead. Well, presumably. I don't think anyone will really be missing her, though.
(Picture courtesy of Matt.)