Here's what the Soviet historian and Bolshevik revolutionary Yemelyan Yaroslavsky had to say about Nechayev in his book "History of Anarchism in Russia" in 1930's:
Nechayev
Before passing on to the Narodnik movement in Russia, which adhered to Bakunin's views, we will deal with Sergey Nechayev, a prominent figure in the revolutionary movement, a man of great will-power, of iron endurance and undoubted organizational ability, and the first advocate of Bakunin's anarchist views in Russia.
Why deal with Nechayev?
Nechayev carried on his activities in the late sixties and the early seventies, when the First International had already been established and the profound difference between the views of Marx and Bakunin had taken definite shape. Nechayev acted on behalf of Bakunin.
We shall not dwell on the struggle over Nechayev that took place between Marx and Bakunin. Abroad Nechayev behaved in such an adventurist manner that not only did Marx suspect him of being a provocateur, but Bakunin himself repudiated his plans (for example, Nechayev proposed that the anarchists raid banks and similar institutions in Switzerland).
In Russia, Nechayev established an organization called the Popular Retribution. This organization was centralistic from top to bottom. All authority was vested in its Central Committee and unquestioning discipline was enforced. It was the most authoritarian organization ever established by revolutionaries. And yet Bakunin, as every anarchist knows, was an enemy of authority. The anarchists still call themselves libertarians, as distinct from the Communist parties. The Communist parties are based on the principle of democratic centralism, i.e., the election of all the leading bodies from the bottom up and the subordination of all members of a lower Party organization (circle, group or nucleus) to the decisions of the superior elected Party organization. The anarchists have always disagreed with this feature of Communist organization. One of the questions on which Bakunin waged a bitter struggle against Marx in the First International was that of how the working class was to be organized.
How, then, could Sergey Nechayev, a disciple of Bakunin, establish a strictly centralized organization and provide it with rules which were utterly in conflict with the official pronounced anarchist views of Bakunin on organization? For decades Bakunin and all his supporters, including his private secretary, Armand Rosse (Mikhail Sazhin), concealed the fact that Nechayev's "catechism" was written by Bakunin himself. After the October Revolution Sazhin related that this "catechism," written in Bakunin's own hand, had been found among Nechayev's papers after the latter's arrest and had been burnt by Sazhin himself. This fact proves that to serve their ends, Bakunin and his supporters were prepared to create organizations so authoritarian and centralized as to crush the will and opinions of their individual members. Such was Nechayev's Popular Retribution, which was broken up by the tsarist government before it had time to achieve anything of importance. The attempts of certain historians to represent Nechayev as a "pretender" whom Bakunin never empowered to act on his behalf are futile. When searching the apartment of a student named Uspensky, who belonged to Nechayev's organization, the tsarist secret police found a certificate signed by Bakunin and given to Nechayev by Bakunin, which read as follows:
”The bearer is a trusted representative of the Russian section of the International Revolutionary Alliance. Mikhail Bakunin.”
It would be wrong, of course, to identify Nechayev with Bakunin. Nechayev has views of his own with which Bakunin did not agree. For example, in Bakunin's opinion the main revolutionary force in Russia were the peasantry and the lumpen-proletariat. Nechayev, however, regarded the working class as the main revolutionary force. In a pamphlet, The Problem of Revolution, Bakunin wrote:
”In Russia the highway robber is the genuine and sole revolutionary – a revolutionary without fine phrases, without learned rhetoric, a revolutionary irreconcilable, indefatigable and indomitable, a popular and social revolutionary, non-political and independent of any estate.”
Nechayev, however, after having lived abroad, and especially after the Paris Commune, became convinced that:
”In the West there are new fresh people to whom the future belongs. They are the workers, divided neither by state frontiers nor by difference of tribe. They are the people who still understand us, for our cause, the cause of the people, is their cause too.”
Nechayev was a consistent internationalist. His good points conflicted with the views of Bakunin.6 But he copied Bakunin's mistaken anarchist views, which prevented him and his young contemporaries from evolving a correct view of the revolution and drove them into narrow conspiratorial activities.
https://archive.org/details/YaroslavskyHistoryOfAnarchismInRussia/