Two players get in a fistfight in the NFL they get fined and suspended, in hockey each team goes so far as to designate an enforcer who is expected to get into fistfights while everyone watches.

NBA a guy throws an elbow he's a serial killer, in Rugby guys kick and elbow while they're on the ground with the ball so they can start the next play faster.

I was just watching some NRL Rugby match and a guy with no pads, no helmet knocks himself out hitting another guy with no pads and no helmet. After a minute or two he stumbles to his feet so the trainers run off the field and play begins again. No concussion testing, no out for a play, just shakes it off and keeps playing.