I'm going to call a friends fiance 'weak fiance'
Why do you want to insult your friend's fiance?
Because I resent that she is taking my friend away, I would like him to be with me anyway.
There is no reason to call someone a name just because you don't really like them. It's your friends partner and they are allowed to choose to date whoever they want to without asking you. Have you thought about talking to your friend about this situation?
It's not my friend, it's his choice, I just feel depressed whenever I see them together and I needed to hurt her.
It's understandable that you have feelings for your friend that's hard to ignore. However, you should not attempt to ruin your friend's happiness by insulting his fiance. You could put him in a position to have to end your friendship.