What should we do with Mean people

Hi Brooke, I have a hard time with my co worker. He is really mean and try to manipulate people through his benefit. Besides of many thing he is doing to get closer to our boss, he is married but he is also with another person in my office.
I feel so bad, I separated my project totally from him.
I wanted to do a model, I wanted to go and ask my boss to sit with all of us separately and ask about our progression in our work individullay since he is reporting to him all the progression on his side.
But my question is if we don’t show them the truth or If I don’t tell the truth to my boss, It means I let the mean people go up n make the world miserable.
Am I right?
Please help me what should I do? How I can model this?