I think I want to hurt my ex-gf.
Why would you want to hurt your ex-gf?
She killed something inside of me
You should cut her out of your life completely so you won't be having these negative thoughts. It's very detrimental to your mental health and you shouldn't want to hurt anyone because that is not normal. Hurting people can get you arrested.
You never liked her so I don't care what you think
I just think hurting people is wrong and you should just forget about her completely.