Nearly every time a fight or incident breaks out in a sport, there are countless people (mostly seen here IMO), that proclaim the player should be charger with an actual crime such as assault. Are there any examples of this happening before, in any major sport? What would it take for it to happen?

The was a boxer who, after the fight, when he lost and had his gloves removed, came over and sucker punched the winner. He was arrested, charged with assault and battery, and served time.

Here's the thing you need to understand: Yes, there is a waiver that is signed that removes liability of players and league for injuries...within reason. If something is out of the area of reason, like a Browns player hitting a Pittsburgh QB over the head with their helmet, they could easily be charged.