I hate this particular friend of mine.
Why do you hate your friend? What did he do to you?
I constantly think of all the bad things he has done to me.
If this friend keeps harming you it might be best to break off the relationship. You should talk with your friend and tell them how you feel.
I'm not nice and I will do what I want to do and I don't care if you disagree.
You shouldn't not care about what I say as I am only trying to give you advice. I suggest you also care about what your friend's opinion and feelings as you should talk to him and make sure that you resolve your issues with him, as it is harder as we grow older to gain friends, and it's even harder to keep the friends that we already have.