Not combat sports in general, but the combat sports where hitting the head of the opponent is a valid method for winning.

Boxing is by far the worst from this point of view, much worse than the combat sports that allow knock-outs but also have other alternatives, like MMA.

Combat sports like judo or fencing are much safer than American football.

It shocking how different Olympic boxing is from pro boxing. Almost all Olympic style bouts finish and are decided on points, whereas pro boxing is primarily about inflicting damage, most often to the head to score a KO.