Sergey Nechayev

Sergey Nechayev (2 October 1847 – 21 November or 3 December 1882) was a Russian revolutionary terrorist.
He was a leader in the Nihilist movement and known for his single-minded pursuit of revolution by any means necessary, including murder.
"Catechism of a Revolutionary".
Nechayev was the author or main author of a famous revolutionary pamphlet, called the "Catechism of a Revolutionary". The pamphlet bears the name of Mikhail Bakunin, a well-known anarchist, but it is thought all or most of it is by Nechayev. The work called for total devotion to a revolutionary lifestyle. "The Catechism of a Revolutionary" argued that any means (including blackmail and murder) could be used to advance the cause of revolution.
It was published in the "Government Herald" in July 1871 as the manifesto of a secret society.
"Catechism of a Revolutionary" was a program for the "merciless destruction" of society and the state. The main principle was "the ends justify the means". This became Nechayev's slogan throughout his revolutionary career. 
Bakunin.
Nechayev and Bakunin knew each other, and Bakunin called him "my boy". All the same, Nechayev was dangerous, and Bakunin was somewhat afraid of him.
Dostoyevsky.
Nechayev's ideas were the basis for Dostoyevsky's "The Demons" (aka "The Possessed"). Dostoyevsky had himself been a young nihilist, and spent ten years in a Siberian labour camp as a result. He came back a determined enemy of everything Nechayev believed. "The Demons" is a "dark comedy, cruelly funny in its depiction of high-minded intellectuals toying with revolutionary notions without understanding anything of what revolution means in practice".
Nechayev's fate.
Nechayev planned to kill a student, Ivanov, who questioned his ideas. On 21 November 1869, Nechayev and several comrades beat, strangled and shot Ivanov, hiding the body in a lake through a hole in the ice. The student's body was found and Nechayev fled the country before he could be arrested.
In August 1872, Nechayev was arrested in Zurich and handed over to the Russian police. He was found guilty on 8 January 1873, and sentenced to 20 years of hard labor for killing Ivanov.
He died in his prison cell in 1882.
Assessments.
It has been said of Nechayev: "His personality and ideas portray, as if in a crooked mirror, the lust for revolution reaching even beyond political fanaticism into insanity. With Nechayev we are already beyond Lenin, [and] so criminal as to forecast the darkest incidents of Stalin".
Biographers of Lenin have said that Lenin put into practice what Nechayev had taught. There is clear evidence in Lenin's own writing that this is so.