he is known as Bloody Feliks which sums it all up
It seems that he was a more complex character, than the way he's been popularly remembered. I was surprised to read in his wiki biography, what Pilsudski wrote about him in his memoirs: "[He] distinguished himself as a student with delicacy and modesty. He was rather tall, thin and demure, making the impression of an ascetic with the face of an icon... Tormented or not, this is an issue history will clarify; in any case this person did not know how to lie."
In other places, he is described as a peculiar murderer, in that he wasn't driven by any of the usual impulses, i.e. lust for power, or banal cruelty/sadism. The consensus being that what defined him was his fanaticism. Now whether this makes much of a difference is a different question.
It's interesting to me that you say he is remembered in Poland as Bloody Felix, when in fact he spent very little time involved in Polish affairs, and for most of the duration of him being a member of the Soviet government Poland was an independent entity outside of his reach (remember, he died in 1926). I thought that the Polish people may have a sort of grudging respect for a former compatriot that had laid the foundations for one of the most powerful and feared intelligence agencies of the 20th century. On the other hand, another thing he is famous for is being a Great Russian chauvinist and an opponent of the right for self-determination for the varied peoples of the Russian Empire. Even Lenin once accused Dzerzhinsky of crass Great Russian chauvinism, to which Dzerzhinsky replied: "I can reproach him (Lenin) with standing at the point of view of the Polish, Ukrainian and other chauvinists."
It's quite hilarious imagining Lenin, a Russian, accusing Dzerzhinsky, a Pole, of being a Russian nationalist and getting "well you're a Polish nationalist" thrown back at him!