10 X-Men Villains With The Biggest Body Counts

Cassandra Nova is an astral parasite that feeds off the life-force of psychics. When Charles Xavier was still in the womb, Nova used his psychic energy to materialise beside him. Charles instinctively knew Nova was an evil presence and so, strangled her.

When this fight caused Charles' mother to go into labour, she was rushed to the hospital. Although Nova's foetus was considered a stillborn, she survived. Since she hadn't fully formed, she spent decades building a body and planning to destroy her "brother's" life.

Because Professor X envisioned a world where humanity and mutants live in peace, Nova thought the best way to get back at her sibling was to desecrate this dream. After tracking down Bolivar Trask's cousin, Donald, Nova used his DNA to activate a mutant-killing machine called the Wild Sentinel. After Nova sent the android to the mutant island of Genosha, it launched an attack which resulted in the death of over 16 million mutants. Because she exterminated 99.9999% of all mutants on Earth, Cassandra Nova brought mutantkind to the brink of extinction with this one single assault.