Hamartia - A Fatal Flaw:

Hamartia is a word from ancient Greece, meaning a fatal flaw. For a character to be interesting, there must be some tragic failing. Imperfection is hard to relate to, but we can sympathize and secretly cheer someone struggling to overcome their weaknesses because we've all been there.

For example, in The Fault In Our Stars, the main character points out a fatal flaw in a guy that she recently met:

The whole thing where a boy who is not unattractive or unintelligent or seemingly in any way unacceptable stares at me and points incorrect uses of literality and compares me to actresses and asks me to watch a movie at his house. But of course there is always a harmartia and yours is that oh, my God, even though you HAD FREAKING CANCER you give money to a company in exchange for the chance to acquire YET MORE CANCER. Oh, my God. Let me just assure you that not be able to breathe? SUCKS. Totally disappointing. Totally.

Do you have a fatal flaw? I have a few. The ones I'm willing to admit to are greed and laziness. I'm always trying to take shortcuts. You would think I would learn.