The X-Files: 10 Best Characters Who Appeared After Season One

Alex Krycek is one of The X-Files' biggest villains. As a double agent who ended up serving himself above all others, Krycek was a constant foil to Mulder's neverending search for what happened to his sister, as well as what the governments of the world are trying to keep hidden.

Originally introduced in season two, Krycek appeared after the death of Mulder's Syndicate informant Deep Throat. Krycek at first seemed to be a charming companion to Mulder, but then it was revealed that the whole time he was a double agent working for the Cigarette Smoking Man.

Krycek would eventually betray Mulder, and even end up betraying his own bosses the Syndicate. Krycek seemed to focus entirely on saving himself above anything else, selling his deadly skills and knowledge of the alien colonization plan to whoever could offer him power and safety.

Krycek would even lose his own arm after fleeing into his native homeland of Russia. He would continue to be a threat even after his supposed retirement, showing up once again in the 2000s to try and save Mulder from an alien virus.

But Krycek's never-ending schemes and almost cockroach-like ability to survive came to an end when he was fatally shot multiple times by Director Skinner, a satisfying end to a truly despicable villain.