Just as Faustus refuses to take religious issues seriously, he laughs at the parade of the Seven Deadly Sins in Act 2, Scene 3 of Doctor Faustus. But really, buddy, they're no laughing matter, which becomes all the more clear when the Sins start to tell Dr. F a bit more about themselves. This parade of sins should be a warning to Faustus to repent, but he has already decided he'd rather serve the devil than God, all so he can grab himself some wealth and power before his soul hits the road. Sounds like sin to Shmoop.
Doctor Faustus portrays pride as the sin at the root of Faustus's fall. If he hadn't been so full of himself, he never would have sold his soul to the devil.
A whole boatload of sins, among them pride, covetousness, and despair, all work together to bring about Faustus's fall.