The fact that he was ostracised by the Leninist faction, forced into exile, and eventually murdered in 1940 by the Stalin regime should tell us a lot about his differences from those two extremely violent communists.
As early as 1905, he propounded a theory of socialism that brought the middle and working classes together in a revolution to make the former more socially responsible and the latter more culturally aware. For Trotsky, social, community and national development was about involving everyone. He was against the show trials, mass imprisonments and murders and the exiles of the bourgeoisie.
Only now, 70 years after his murder, is it becoming clear that Trotsky was a man of intellect and principle, with a strong sense of humanity and social purpose.
By the way, be careful if you read any books on the subject written by Robert Service, who seems determined to show that Trotsky deserved to die; no matter how horribly and at whose hands.