Actually, an intelligent person would know that "revenge" is a transitive verb; therefore the sentence, "weak people revenge" is grammatically incorrect as it requires one or more direct objects on which or for which these weak people may seek revenge.
Stay away from negativity! Don't feel bad for doing it. If a person is mentally and physically draining, don't let them play the victim card and get you to stick around just to be abused. Get rid of that person.