Megalomaniac Troll
A person exhibiting megalomania, and suffering from the online disinhibition effect. The 'Megalomaniac Troll' usually hides behind anonymity and minimization of authority, usually achieving psychological Catharsis. Since any personality type is allowed on the internet we begin to see more of a societal breakdown.

Megalomania is "a psychopathological condition characterized by delusional fantasies of wealth, power, or omnipotence", according to The Corsini Encyclopedia of Psychology.

Megalomania and the online disinhibition effect could be theoretically characterized as: 'a condition characterized by delusional fantasies of wealth, power, omnipotence, and the purification and purgation of emotions'. Theoretically, this, in turn could make the sufferer exhibit real world behavioral issues or complications, such as sociopathy or psychopathy.

Simply put: The 'Megalomaniac Troll' is a person online who believes they are superior in all walks of life, from mental superiority to physical and wealth superiority.
Real example - warning graphic:

Young girl: i like love this song

Megalomaniac Troll: Kill yourself nobody loves you and you're ugly.
Bystander: as if you woudl say that to her whats your prob dude? wtf
Megalomaniac Troll: As if you would say that to her, what's your problem, dude, WTF? * IDIOT! KILL YOURSELF