I'm probably way off the mark here.. but I've been kicking around an idea of what came before what to create what in the Fantasy genre.
And since we were specifically talking so much about "Gritty" fantasy with its anti-heroes or outright villainous protagonists I wondered where exactly it came from.
And though I'm not 100% certain, I think the first example of Villainous Protagonist in a fantasy novel I can think of is probably Steerpike, in Mervyn peake's Gormenghast Novel. I know many have argued that the castle itself is the main character.. and I don't doubt that.. but Steerpike is the main POV character for the first novel, and revels in his destruction in the second novel as he plots on how to continue it.
I suppose you could go back further, and try to lay the claim at the feet of any of the Nordic Outlaw tales.. But simply put.. most of those guys despite being outlaws still wind up doing something Heroic. Egil Skallagrimson winds up doing heroic things on multiple occasions even.. Those are more along the lines of the traditional view of the "Anti-Hero" But Steerpike... never does anything unless it helps Steerpike, will kill anyone who gets in his way or once their usefulness is ended to him. Theres a lot of Steerpike in the works of K.J.Parker..
It seems odd though to blame it on Mervyn Peake. The stories themselves aren't to blame, and neither is the author.. since after all.. the second book in the series climaxes and ends roughly as a typical Fantasy novel would. Since thats the case it proves then that a great many people don't really pay attention.. Steerpike is the on again off again main POV but he's not the main character of the story.. Titus is, Titus is the hero of the story. And Steerpikes murdering and larcenous behaviors simply led to Titus becoming that hero and dispatching Steerpike the villain. But it's easy to see how people, especially if they didn't really like the first novel in the series.. might get the idea that Steerpike is the one they should care about.. rather than seeing him as what he is.. the snarling beast outside of the circled wagons looking for a way in. They instead seek to try and out do him for his behavior and see how much further their own character can go.
I think that, Peake's Steerpike, rather than Donaldson's Thomas Covenant, who though clearly an asshole who rapes a woman.. then regrets it and wallows in self pity.. that dosen't sound much like the characters in these modern books.. But Steerpike knows no shame and it is he who is the seed which germinated into what we now see as 'Gritty' fantasy.
And while Joe Abercrombie has been the center of a lot of the maelstrom surrounding these discussions lately.. I'm going to state that though he plays with some of these ideas.. I think his work is simply a more traditional fantasy series.. albeit one which he is trying to deconstruct.. it's up to the reader to decide how well he did with that task. However, that said, I feel that Peake, is an enormous influence on K.J.Parker.