Designing the worst Internet user? Hmm, that's an interesting challenge.
He lives in his elderly parents' basement. He maintains accounts on many sites, including popular sites, quieter sites, and even the corners of the Internet that not even the 4chan trolls want to visit.
His diet consists of nothing more than high-fat, high-caloric junk food and soda. Normally, this wouldn't be so much of a problem if one consumes only moderate quantities, but he eats about five to seven "meals" of Cheetos and Mountain Dew a day.
He holds many opinions, none of them informed, all of them only to be contrary to everyone else he perceives as the majority. He is easily one of the most extreme of every group he's in.
His political views are acidic and pathetic. He doesn't hold debates, he merely flames the opposition until they give up, and then he perceives those "debates" as victories, further enforcing his viewpoints. He is incredibly progressive, but only up to the point where it affects him personally, and then he sounds like a Tea Partier on meth.
He trolls the Internet day in and day out. Many times he loses track of time, leading to literal days of browsing and surfing and trolling. He has no friends, even among other trolls, because he talks down to everyone. He puts forth no attempt to even seem like a nice person, not even at first. He is banned from so many websites and forums because of his caustic posting habits. He was so bad that administrators of various webforums would pass around his preferred username and e-mail address, and they would ban him before he even registered an account.
His websites were removed for hateful content. His posts were deleted on sight by even the most lenient moderators. He once even cleared the official #linux because the users couldn't stand him. His YouTube comments are always marked as spam and have hundreds of thumbs down; his videos are hand-deleted by YouTube Moderators themselves. Spammers don't even send him spam.
He is the worst user of the Internet.