Honestly? Bluespike, because of how polarizing he was, or Liquid Chris. Least favorite is the Asperchu Four or Clyde Cash.
I get how horrific what he did was to Chris, and while at the time I thought it was hilarious, once I got out of my edgy, angry teen phase (was 16 when it happened) I realized how fucked up it was. But after the revelations of him engaging in dubiously consensual incest - I honestly can't decide if, from what we know of Barb, if it was consensual or not - and the whole list of other bullshit he's been doing... Fuck it, Bluespike is hilarious again. Plus, in all honesty, I don't think Bluespike damaged Chris' psyche / mental state all that badly once
Liquid Chris was interesting, but Kasey ruined a lot of the hilarity by not shutting her fat mouth. Liquid and Solid going at it was hilarious, but Kasey kept shouting over them and telling them to 'stop'.
While Alec did a half-decent webcomic to fuck with Chris, the fact that they went out of their way to fuck with CWCville revealed to every insane ween that 'If I can fuck with CWCville Chris thinks it is real and it hurts him badly' is pretty shitty.
Clyde Cash was, what, 30 different people from the "PVCC", and that 'forum' was pretty gay, especially when compared to the CWCki forums - One became infested with troons and the other became the Kiwi Farms.