Ctrl-Alt-Del: Just a really average gaming webcomic. Creator's got a bit of an ego but he's gotten a bit better about some things over time (he finds the Loss memes more amusing now than he did when it first began, and to be fair his art nowadays is way better than it used to be).

Assigned Male: It at least tries to give a good message about being supportive of transpeople, but the way it presents its message isn't the best, even other transpeople find it annoying.

Rockyeet: If the dude himself wasn't a literal nazi maybe a small few of his comics could have some merit but in general the dude's a real asshole.

Dobson: Hated even by the people who he once associated with, as even inflation artists are like "geez, that asshole? Even when he was affiliated with us he was still a jerk." Basically he's just disliked by many, hardly anyone would ever say they legit like his stuff.

I think I can take a crack at the "why" for each:

Awkward Zombie: Sticks strictly to video game humor and is pretty consistently good, the creator doesn't really try and piss people off.

VG Cats: Some comics can be hit-or-miss with their humor but overall its main two characters are considered pretty likable and cute.

Cyanide and Happiness: Purposely crude art and sometimes likes to go for something dark rather than humorous, but is still enjoyable for the most part.

KC Green: Makes amusing comics that still have messages sometimes.

Sarah Scribbles: Sticks pretty much solely to comics about relatable matters; not everyone's cup of tea but the way they're presented may be enjoyable to some.