The fatal flaw of Doctor Faustus is pride. This sin is the cause of Faustus" damnation. Faustus committed many sins, but they all revolve around the one sin of his excessive pride, or hubris. In Greek tragedies, hubris causes the wrath of gods to come upon one, which is what happens in the case of Faustus; his desire to be a God is a sin in the Christian religion. The fact that Faustus wants to be an equal with God prevents him for asking forgiveness from God. Faustus is in total denial of God's power, his pride refuses to let him realize how powerful God really is.
Lucifer and Faustus have much in common once one thinks about it. Lucifer was thrown from heaven by God because of his pride and insolence. Faustus rebels against God, just as Lucifer did. Faustus is the same way as Lucifer was, therefore will be damned in hell just as Lucifer is. It is his strong pride that damns him. .
Faustus looks forward to hell and does not believe Mephistophilis after he answers all of Faustus" questions about hell. His pride does not allow him to accept the truth and he then makes up his own thoughts about the place. Hell is not the type of freedom Faustus hoped for, it is only a burden for those who have sinned. .
At the end of the play, Faustus is no longer proud, he fears his death and is also afraid to turn to God after all he has gone through. Faustus does not want to go to hell, but he is doomed all because of that one flaw: Pride.