John Brown (1800-1859) who is best remembered in the failed raid at Harper's Ferry, West Virginia, during October, 1859, can be considered to be both hero and villain.
Certainly he was a man who lived by his convictions, having publicly sworn in 1837 that he would "abolish slavery," becoming a prominent figure during "Bleeding Kansas," and ultimately driving him to attempt an armed rebellion. During his trial, he rejected his defense counsel's suggestion of an insanity plea which might have spared him from hanging, as he felt that such an admission would morally invalidate all he had done, and weaken the cause of Abolition.
Although his commitment to the cause of Abolition could be considered heroic, perhaps the extremity of his actions transformed him into a villain -- murdering several pro-slavery settlers during the "Bleeding Kansas" years, killing innocents during the heat of battle during the Harper's Ferry raid, and attempting to incite an armed rebellion in which slaves would kill masters.
Curiously, Brown is one of the few people ever convicted for the crime of treason in the United States; the US marine troops that surrounded Brown and his followers at Harper's Ferry were commanded by Robert E. Lee, and under Lee's command was militiaman John Wilkes Booth.