@fBoyle-- That's a good question. Aside from the story being about the protagonist (sometimes called "hero" or heroine"), I do think that tragic protagonist all have some common qualities. Aristotle said that a tragic protagonist must be someone that the audience pities or fears. So if the protagonist is the victim of fate, the audience will pity him, whereas if he makes his own fate, the audience fears him. It's also possible for the tragic protagonist to invoke both types of feelings.
For example, I saw a tragedy film recently where the tragic hero was left fatherless as a child by an evil man who hanged his father. The boy grew up to take revenge for his father's death and killed his murderer and his friends. But he also ended up dying in the process. Throughout the film, I sometimes pitied the character and sometimes, seeing him take revenge, I feared him. I think this is a good example of a tragic protagonist.