|Jake LaMotta in Raging Bull|
It's not about the characters' actions. It's about what the author is trying to say about their actions, otherwise known as the themes of a work. Far too often in modern literature, themes are neglected in favor of style. Readers seem to prefer formula over originality, and style over substance. This is why so many best-sellers today feature some generic guy with a six-pack on the cover. It's a sad day in the world when so much weight is placed on whether or not the characters were "hot enough".
Whatever happened to ideas?
Jake LaMotta (as portrayed by Robert DeNiro) is a thoroughly unlikeable, despicable character. But that doesn't make Raging Bull any less of a masterpiece. It's a treatise on violence in modern society, both as entertainment and as a means of conflict resolution. LaMotta is a man who works in both. He is flawed. He is human. That's what makes him interesting.
Holden Caulfield is another character commonly referred to as "unlikeable". Goodreads currently lists 48,601 one star reviews for The Catcher in the Rye, almost all of the naysayers complaining of the "whiny" Caulfied. Did the readers forget that this is a book about a conflicted teen? This is how teens act. They whine and complain, and they act immature. The character is an accurate reflection of reality, and for me, this is infinitely more interesting than reading a book where all the characters are flawless and inhabit some fairytale land where everyone is cute and nice.
But hey, that's just my opinion.