The 'Jonah Hex' actor stars as a man suffering with writers block and experiencing marital problems with his wife, played by Naomi Watts, and he confesses he thinks of him as a "sad" man.
He said: "It's like a fog of war. He's a sad character to me. He's funny sometimes, but he's a sad character.
"I just wanted to slap him. I hated him. I didn't love to play him."
The 43-year-old actor gained considerable weight for the role which he has since lost, something his wife Diane Lane is not fond of as she prefers a larger man.
He told The Scotsman newspaper: "She loves it. She loves the big bear. She loves it when I have my beard and she loves me when I'm big."
Despite his now successful career he has not always had big hits, and Josh recently revealed he was not proud of 'Jonah Hex' because it became "derailed".
He said: "We had an original intention and that got away from us.
"It got so derailed at a certain point that the assemblage of what we could use was so disconnected to what our original intention was that it just got mixed up.
"I still think it's a lot of fun. If you go in there, kind of like 'Piranha 3-D', when you go and see that movie and you go and think, 'This is ridiculous,' and, 'This is fun,' then you could still go in there and have a good time."