Madame Hydra

Viper is a high-ranking member of HYDRA and leader of the Serpent Society.

Physical Appearance
Viper is a tall woman with a voluptuous yet well-toned built, broad shoulders, and long dark green hair, which covers the right side of her face. She has dark green eyes. She wears green lipstick and maintains green wardrobe as well. She also has mysterious scars on the right side of her face, which she hides with her hair. She is shown to be very well-endowed.

Personality
Viper shows to be very hateful to anyone who are against HYDRA. Her scars caused her to have such personality. In desperate times, she was willing to work with her enemies to get things done and remind them that after it's over, she'll resume her hatred again.

The Avengers: Earth's Mightiest Heroes
Viper's early life is shrouded in mystery, but it is implied that something happened to her, which gave her scars on the right side of her face and made her hate people like Captain America. She eventually joined HYDRA and acted as one of Baron Strucker's right hand lieutenants. During his time, Viper heard rumors of the Serpent Crown, which would give her the power to conquer the world in order to impose their new world order, using HYDRA to seek the crown, but without any success. At some unknown point, Viper was captured and supplanted by a Skrull who infiltrated into the HYDRA ranks. The Skrull's capture was Nick Fury's first hint of an upcoming Skrull invasion.

Ultron also pretended to be Viper, giving radio orders to the Serpent Society to keep the Avengers busy.

The actual Viper was the first of the Skrulls' prisoners Captain America found when he was escaping himself. They freed the other prisoners (one of them her second-in-command King Cobra) and escaped together, with Viper even taking Cap onboard the escape ship when it seemed he was going to be left behind.

After the Skrull invasion was over, Viper and King Cobra were transported as prisoners by armored truck, but the rest of the Serpent Society arrived to break them out, which resulted on them trapped in the subway alongside Captain America, Spider-Man and civilian bystanders. Cap and Spidey managed to protect the bystanders from the Serpent Society.