“There are times when the interests of the proletariat call for ruthless extermination of its enemies in open armed clashes.”

“Lessons of the Commune”, in Zagranichnaya Gazeta, No. 2 (23 March 1908) http://www.marx.org/archive/lenin/works/1908/mar/23.htm, as translated by Bernard Isaacs, Collected Works, Vol. 13, p. 478.
1900s
Variant: The proletariat should not ignore peaceful methods of struggle — they serve its ordinary, day-to-day interests, they are necessary in periods of preparation for revolution — but it must never forget that in certain conditions the class struggle assumes the form of armed conflict and civil war; there are times when the interests of the proletariat call for ruthless extermination of its enemies in open armed clashes. This was first demonstrated by the French proletariat in the Commune and brilliantly confirmed by the Russian proletariat in the December uprising.

"Resolution on Party Unity" (May, 1921)
1920s

Preface; Previous Attempts Miss the Point.
1930s, On the Rocks (1933)
Context: The extermination of what the exterminators call inferior races is as old as history. "Stone dead hath no fellow" said Cromwell when he tried to exterminate the Irish. "The only good nigger is a dead nigger" say the Americans of the Ku-Klux temperament. "Hates any man the thing he would not kill?" said Shylock naively. But we white men, as we absurdly call ourselves in spite of the testimony of our looking glasses, regard all differently colored folk as inferior species. Ladies and gentlemen class rebellious laborers with vermin. The Dominicans, the watchdogs of God, regarded the Albigenses as the enemies of God, just as Torquemada regarded the Jews as the murderers of God. All that is an old story: what we are confronted with now is a growing perception that if we desire a certain type of civilization and culture we must exterminate the sort of people who do not fit into it. There is a difference between the shooting at sight of aboriginal natives in the back blocks of Australia and the massacres of aristocrats in the terror which followed the foreign attacks on the French Revolution. The Australian gunman pots the aboriginal natives to satisfy his personal antipathy to a black man with uncut hair. But nobody in the French Republic had this feeling about Lavoisier, nor can any German Nazi have felt that way about Einstein. Yet Lavoisier was guillotined; and Einstein has had to fly for his life from Germany. It was silly to say that the Republic had no use for chemists; and no Nazi has stultified his party to the extent of saying that the new National Socialist Fascist State in Germany has no use for mathematician-physicists. The proposition is that aristocrats (Lavoisier's class) and Jews (Einstein's race) are unfit to enjoy the privilege of living in a modern society founded on definite principles of social welfare as distinguished from the old promiscuous aggregations crudely policed by chiefs who had no notion of social criticism and no time to invent it.

The Beast of Property (1884)

As quoted in The Myth of the Nation and the Vision of Revolution: The Origins of Ideological Polarization in the 20th Century, Jacob Talmon, University of California Press (1981) p. 487
Undated

Han Kuo-yu (2019) cited in " Kaohsiung mayor departs for visit to Malaysia, Singapore http://focustaiwan.tw/news/aipl/201902240005.aspx" on Focus Taiwan, 24 February 2019.
2019

Message to Linux kernel mailing list, 2009-03-25, Torvalds, Linus, 2009-03-25 http://lkml.org/lkml/2009/3/25/632,
2000s, 2009

As quoted in Three Faces of Fascism: Action Française, Italian Fascism, National Socialism, Ernst Nolte, New York: NY, Holt, Rinehart and Winston (1966) p. 156. Opera Omnia di Benito Mussolini, V, p. 121
Undated