The "bathroom" scene (spoilers)
I've seen this movie many times and I always wondered: is there any other evidence of Costner's TRUE feeling for Susan other than the scene in Gene Hackman's office when he first finds out who the dead girl is? He excuses himself, goes into the bathroom, and falls to the floor. That was a private moment of grief.
Last scene he screams "You wanted me to be her lover, I was her lover!" So...w/o the bathroom scene, he could have been faking every single moment in the movie. Was there any other "proof" that Costner was just not using Susan to get to Hackman aside from the bathroom scene?