My least favorite Marvel artists are (in no particular order):
Rob Liefeld has no idea of human anatomy
Eric Canete's humans have zero bones out of 206
Humberto Ramos: I just don't like his style.
John Romita Jr draws characters in a way that really bugs me out. I actually liked some of the guy's work in the 90s. And the ones where he penciled and his father inked were absolutely great. Later, he changed his art style and now we're left with this. Again, it's a personal preference, but I don't like the art style.