Madame X was a Hungarian patriot and spy who posed as Comrade X.
She initially operated in the U.S., where she was the second foe Henry Pym encountered as Ant-Man, she disguised herself as a man and tricked Ant-Man and nearky poisoned him so he couldn't foil any more communist plots but she was stopped by Ant Man's Ants.  She was deported to Hungary where she joined the newly-formed Bratislava Complex. Her duties expanded to running the entire Project and acting as head of the People's Security Force, her team of Bratislava-based super agents.
Madame X was both a capable spy on her own and an excellent leader of her super agent team. She was rude, contemptuous, and combative toward her opponents, perceived criminals, and anyone from the West. She had a burning hatred of Henry and Maria Pym.
Madame X possessed no superhuman abilities, and often wore body armor and used a poison gas gun in battle.