What (if anything) is Hamlet's fatal flaw?

Concerning Shakespeare's Hamlet, I'll
put my vote in for Hamlet's tragic flaw being hubris.  Hamlet has an opportunity to get
his revenge and kill Claudius, but hubris keeps him from doing
so.

Claudius's reaction to the murder scene in the
play-within-the-play convinces Hamlet that the Ghost is telling the truth and that
Claudius is, indeed, guilty of killing King Hamlet.  Once he's sure of Claudius's guilt,
Hamlet seems ready to kill the king.  He has a perfect opportunity to do so while
Claudius is praying, but decides not to because he doesn't want to send Claudius
straight to heaven.  Hamlet thinks Claudius is confessing his sins, and killing him when
his slate or soul or whatever is clean, Hamlet believes, would send Claudius to heaven. 
Hamlet won't do that. 

When Hamlet makes the decision not
to kill Claudius for the reason he gives, he is stepping beyond his station in life:  he
is guilty of hubris.  Human salvation is not Hamlet's business--it's God's business.  If
Hamlet kills Claudius in Act 3, numerous innocent lives are saved, including his own. 
His hubris leads to the blood bath at the conclusion of the
play. 

Ironically, Claudius is not confessing his sins.  He
is unwilling to give up the spoils of his sin, and won't repent.  Thus, Hamlet could
have killed Claudius in Act 3, gained his revenge, and not sent Claudius to heaven. 
Unfortunately, he gives up the chance to do so.  This, I believe, is the climax of the
play and reveals Hamlet's tragic flaw.