Boxing, judo, jui-jitsu, tae kwon do, football, lacrosse, even soccer.
Potential serious injuries. Or girls gymnastics, actually, the most injurious.
The reality is it all depends on the rules instituted and enforced for the matches. Tough call, would I rather my kid was trained and in an MMA match with well thought out combat rules or on the field with the kids of some of the foaming at the mouth parents I’ve seen just screaming win at the kid…