Whatever a man’s color or beliefs, he is still human. You X-Men are not!
~ Stryker, in response to Cyclops asking if he would do the same things to his fellow man that he does to mutants.
William Stryker is a prominent enemy of the X-Men originating in the "God Loves, Man Kills" story arc - he is depicted in the comic books as an insane, sadistic, and heartless fundamentalist televangelist who views mutants as a sin against nature and seeks to destroy them, forming a similar minded group in the form of the Purifiers.
However Stryker's origins were changed in the movie X-Men 2, in which he was a leading member of the Weapon X program that created Wolverine - though he retained his ruthless nature, for the sake of simplicity we shall list the two Strykers as separate entities for the remainder of this article.
God Loves, Man Kills
Stryker is introduced as a religious fanatic with a military history which may have involved the Weapon X project, he is characterized by his intense hatred of mutants - which is so great he murders his wife and son when he finds out he is born a mutant - his sanity shattered he makes an unsuccessful attempt at suicide. As time passes he becomes unhinged further - convinced that Satan is behind the creation of mutants as a means to destroy humanity - Stryker also starts to see the birth of his son as a sign from God to eradicate all mutants.
Driven with newfound fanaticism Stryker becomes a popular but controversial preacher whose followers commit hate crimes against mutants - Stryker then arranged to have Professor Xavier kidnapped, brainwashed and attached to a machine that would kill all living mutants using Xavier's telepathic powers.
The X-Men join forces with Magneto to avert this disaster and Stryker's madness is revealed to the world when he tries to publicly execute Kitty Pryde in front of a television audience - prompting one of his own security guards to shoot and arrest him.
God Loves, Man Kills II
Stryker served a prison sentence as a result of his actions but was rescued by Lady Deathstrike, an enemy of Wolverine, and it was revealed the two were lovers - he immediately began a crusade against the X-Men - focusing particularly on Wolverine, Cannonball and Shadowcat - who he hated the most.
However when his followers brought Kitty Pryde to him she seemed to be able to get through to the madman and convince him that mutants were not the monsters he thought them to be - her words seemed to have an effect on Stryker and he seemed to repent.
However after the Decimation event following the House Of M story arc Stryker's fanaticism rose again - viewing the massive loss of mutants as a sign from God to end them as a species - he pretty much called for genocide on TV and appeared in New X-Men as the main villain - with the help of Icarus (one of Xavier's students) he caused a bus to explode - killing about 1/4 of the depowered students from the academy. He then planned the assassination of Wallflower and tried to kill Sooraya Quadir - the deaths of Wallflower and Dust were Stryker's main objectives since Nimrod had told him that both girls would destroy his army - finally he launched a full-on attack on the Xavier Institute with the Purifiers, killing Quill and leaving both Onyxx and Cannonball critically wounded - after the defeat of the Purifiers Stryker was murdered by Elixir - the enraged boyfriend of Wallflower.
Recently, Bastion has resurrected Stryker with a techno-organic virus to join Bastion's new Purifiers - He was ultimately sliced in half and killed by Archangel when he and his team of Purifiers attacked Hope Summers.