Ramón Mercader

Assassanation
Ramón Mercader was a mexican communist who assassanated Joeseph Stalin's greatest rival Leon Trotsky on August 21st, 1940 at his home in Mexico City, Mexico. Mercader posed as a follower to Trotsky's belifs and befriended him and his guards. When he and Trotsky were alone in his study, he snuck up from behind and stabbed Trotsky to death with an Ice Pick. He was imprisoned for 20 years for the killing.

Motive
His motive was simply he was a Soviet Agent, and Stalin told him too.