I'm going to tell my friend's girlfriend that she should break up with him.
Why would you try to have her break up with your friend?
Because I want him to find another woman more suitable for him.
It is good to care about your friend but you cannot butt in on his relationship. This will cause everyone a lot of trouble and stress.
I don't care if my actions cause drama. I know it's the right thing for him.
If you really feel so strongly about this, you should delicately and calmly explain how you feel to your friend. Intentionally trying to sabotage his relationship will just make him resent you and probably end your friendship with him. It's his life and you should let him make his own decisions.