1. Magneto: Magneto was formerly a friend to Professor X. He stands polar opposite of Xavier’s dream of peace between mutants and mankind. Magneto believes mutants can only be free if they enslave mankind. Magneto has the power to manipulate the planet’s planetary forces, making him one of the most powerful mutants alive. He also is the leader of the Brotherhood of Evil Mutants. Magneto is the perfect archenemy for the X-Men with his intelligence and leadership abilities making him quite the formidable opponent.
2. Apocalypse: Apocalypse is one of the first mutants to be born in the human race. He is also one of the strangest. Apocalypse is a metamorph capable of altering his shape and physical appearance. He can increase in size and acquire practically any mutant power. Apocalypse’s ideology is even more extreme than that of Magneto. Unlike Magneto, Apocalypse believes many mutants are not fit enough to survive. Apocalypse is also endowed with an incredible life span which gives him millennia of knowledge.
3. The Hellfire Club: The Hellfire Club is the opposite of the X-Men. While the X-Men are regarded as unwanted outlaws, the Hellfire Club is society’s elite. While most members of the Hellfire Club believe it is nothing more than a social organization, the inner circle of the Hellfire Club knows better. The Inner Circle is a diabolical group of mutants intent on amassing political and economic power through illicit means if necessary. They are intent on becoming all powerful at any cost.
4. Dark Phoenix: Jean Grey became the powerful telepath Dark Phoenix after she was exposed to radiation in space. This radiation helped her reach her full potential as a telepathic mutant and she changed her costume and name to Phoenix. The mutant Mastermind was able to trick Jean’s mind into thinking she was a part of the Hellfire Club. As the Phoenix, Jean captured the X-Men, and Mastermind killed Jean’s lover Cyclops. When Jean saw the death of Cyclops, she broke through Mastermind’s hold on her brain and renamed herself the Dark Phoenix. As the Dark Phoenix, Jean suffers from emotional strain as she tries to remember her past life, but still struggles to hold the dangerous creature Phoenix within her. Due to her dangerous telepathic powers, the Dark Phoenix makes our list.
5. Sentinels: The Sentinels were created by Dr. Bolivar Trask, a scientist who was also a father of two mutants himself. Trask created these giant metal robots to identify, seek out, and kill mutants around the world. The government feels the Sentinels are necessary in order to keep the mutant race at bay. Throughout the history of the X-Men, the Sentinels have been upgraded countless times by different individuals. With each upgrade, the Sentinels have become more powerful and more difficult for the X-Men to defeat.