What is the worst trait to have?

I think the worst thing to have in relation with Allah is the character that I have: being vengeful. I can not forgive people!!! The doctor who ed me when I was born, I am still looking for him to him back :) LOL but seriously, It's been few years that I am working on being able to forgive people but nothing much has changed:( This was one of my first prayers in this Ramadan and the last Ramadan: to be able to forgive.