Biggest? That is tough, I have so many.
Probably my largest flaw is that I am sex driven. Lots of people enjoy sex. But I figured out early that I was a bit different, as a woman that I have talked to put it, "wound a bit to tight". When I was in the army I talked to a lot of guys about what they liked to do and how it compared to sex. Most guys talked about flying, sailing, scuba diving, rock climbing etc. They all claimed that they would rather do these things than have sex. For me, I only do other things because I am not having sex. It impacts all aspects of my life, relationships, and happiness. I suffer from depression because of it.