This is a good question. Let me give you the most common qualities.
First, a tragic hero must be noble is some sense. A tragic hero cannot be a common person. For example, Oedipus is a ruler and has great qualities. He is wise and brave.
Second, a tragic hero has blind spots. More specifically, he or she lacks self-knowledge. We can say that it is the antithesis of the adage at the oracle of Delphi - "know thyself."
Third, a tragic hero transgresses some boundary and by this catches the notice of the gods or some other person in leadership. This transgression may also be seen as a breaking of the adage of Delphi - "nothing in excess." We can call this hubris.
Fourth, a tragic hero comes to ruin on account of a noble flaw.
Fifth, a tragic hero usually sees some sort of redemption in the end and certainly elicits sympathy from the audience or reader.