In the last 2 years, hands down there is no question. Of course it is 2Q1C of chess.com fame, known by another name here. Not seen today, because he can't resist trolling CC ! Opened a 1/2 dozen accounts today; among others ... iDONTremeberCanyou and RichBLM Queen. Current one is UrkelJerkelChess, playing the victim as a poor, gay, under-privileged black kid. Shouts insults, then plays the victim of homophobia and racism. The accounts remain open briefly, soon get banned. The "dude" is a work of art. Has most posters up in arms with the usual mocking comments. Yep. The most "infamous". CC seems incapable of blocking the creation of new accounts at will. A conservative estimate is 1000 accounts in 2 years. 2Q figured out how to re-activate old, unused accounts. An obscure email server that sent new passwords on request. Had staff and members fooled for month's ! (Well, not everyone ;-) 2Q was appearing with accounts from 2009 !
The real problem is: The intent is malicious. It's not simply fun and games, as his followers portray. The mocking of the disadvantaged, the general chess community, staff and respected chess professionals, is the work of a disturbed individual.