We only have to spend four chapters with Albert's drunk father, but that's more than enough to realize we don't like him.
Before you can say "Natty Light", this guy has tried to whip Joey into shape (with an actual whip), threatened to shoot him, and sold him to the military for forty pounds. We don't even know his name—only that he's Albert's dad, and he's perpetually soused.
Of course, if it weren't for him, we wouldn't have a book. It's Albert's drunk daddy who buys Joey in the first place. Albert and Joey form a life-long bond despite his father's belief that "[horses] are stupid creatures. Obstinate and stupid" (1.14). To which we say, takes one to know one, buddy.
Okay, maybe we're being a little harsh. He's doing what he feels he must to get by and to keep his family sheltered and fed. And we have to concede that Albert's dad does two smart things: he sells Joey for a profit and he raises a boy determined to not be like him.
Although we don't see Albert's drunk father at the end of the book, Albert tells us a little bit about him: he's always regretting selling Joey; he's quit drinking; and it turns out he's kind of a nice guy. Albert seems to have forgiven him, proving that horses aren't the only ones capable of forgiveness.