What qualities of the tragic hero does Hamlet have?

I would simply add to this excellent answer that Hamlet has a good reason for being undecided, at least in the earlier part of the play: his chief source of information is a ghost, and he has no way of checking its credentials. The ghost might be the spirit of his father, or it might be a demon sent from Hell to deceive him. Even if it is the former, blood revenge is emphatically not a New Testament Christian value, and so the right of the ghost to command that Hamlet kill its murderer is in question.

From this perspective, we might say that Hamlet is a tragedy because the protagonist has no available course of action that produces morally unambiguous results. The "tragic flaw" is not so much his indecision as his inability to access enough reliable information to make a good decision, combined with the moral imperative he do something about the situation. If he kills Claudius at once, he may be acting under demonic deception and damning himself. If he tries to gather further information, as he does, his actions may spiral out of control (as they do), resulting in the deaths of many others (Laertes, Polonius, Ophelia, and his mother to begin with). No wonder the poor fellow considers suicide.