After reading about him on the villains wiki, I can safely say he's now worse than Plankton. Or is it the writers' fault for ruining the show to this point?
Anyway, here's my opinion on who's the most evil. Not many of you may heard of the Total Drama Series, but the one character I think is more evil than any other character in children's TV shows is Chris MacLean. If you see more of the show, you can see how bad he is. All he loves to see is drama. Every season, he tortures the contestants by making them live in uncomfortable conditions, eating gross foods (although this is more Chef's fault), and allows the other competitors to be mean to each other at any time. He also makes testing his challenges very unsafe for interns. None of the interns survive when they try to test the challenges he set up. And he only cares about making money by causing drama as this is what he loves more.
Throughout the show, you could see more villainous acts or acts of injustice coming from him. He has a few rules set up, but he sometimes allows others to break the rules. In addition, he gets worse over time. Seasons One and Two show that he's more caring when challenges get really dangerous, but as the show progresses further, he gets crueler and less caring for the contestants. For example, starting with season 3, eliminations became more and more unsafe for the contestants. First, he makes them walk to some vehicle. But in TDWT and beyond, he makes them enter a very dangerous trap as the way to eliminate. Another good example to prove how villainous he was is what he did in TDRotI. He made 13 teenagers live on a radioactive island for some extremely dangerous contests, and was obsessed with explosives. I think that was one of the cruelest things he has done. There's more that he has done, but I can't even believe this guy anymore. He's worse than what the contestants are.