Yes, but I think you would describe whatever it is within himself that is the antagonist. Like, if it's his drinking that's holding him back it would be "So-and-so's alcoholism" as the antagonist.
Take Good Guy Greg. He's obviously a Good Guy, but mentally he's terribly disturbed. Just an example. Demonstrates he's a Good Guy on the outside but on the inside, he's thinking about eating babies. Pro on the outside, antagonist on the inside. He has a tough time not literally eating babies.