It would be easy to say that indeed Sir Thomas More as portrayed in Robert Bolt`s A Man for All Seasons fits that definition of a tragic hero. There are two problems with the easy answer. First, the concept of ' a tragic flaw` is somewhat of a misconception of the notion of 'hamartia' as developed in Aristotle, which is, instead, and irrevocable action (literally an arrow released from a bow that cannot be recalled), and often situational. Next, More is an historical figure with all the ambiguities that implies. Finally, More, as Roman Catholic, standing up against Henry VIII, would have considered his actions as perhaps contributing to eternal salvation rather than damnation. Thus martyrdom would not be considered a tragedy, but rather a momentary discomfort resulting in eternal bliss.
Just as the poster above stated More's inevitable death was one that was a martyrdom as opposed to a tragedy. I believe that More doesn't have a tragic flaw, but merely is a man who feels very strongly about his beliefs. These beliefs include his religious and political views as well as his deeply engraved moral values. These combined are what cause More to make the ultimate sacrifice for his beliefs not a tragic flaw.