Little Nicky

There's Cassius, who's big and strong, but lacks the ''goodness'' to make the job real. There's Adrian, who while really hot (no pun intended) and smart, has no goodness as all. Then there's Nicky who, while having good, lacks any evil whatsoever. As seen in the previews, he is told to release his evil. He needs to release it to save his dad. Cassius and Adrian leave Hell, thereby freezing the wall of fire that lets the damned souls into Hell. It's up to Little Nicky to go and get his brothers, putting them into a flask and bringing them back to Hell at the exact same time to save Satan from decomposition.

The catch is that he only has a week, and that Adrian and Cassius are MUCH more powerful than he is.