Teenage boy with extra Y chromosome beats best friend to death
There was a teenage boy (white skin, possibly had blond hair) who had an extra Y chromosome and had killed his best friend by beating him to death with his bare hands/fists. It may have been a made-for-tv movie (and it may have aired on TBS or USA or possibly even Lifetime). Sometime between 1985 and 1995, I believe.
Comment on Quinn F's post
That looks like it might be the right thing. All these years I've thought it was a movie. (I only saw part of it.)