Having one-punch knockout power in MMA is a very beneficial thing to possess.
You have the ability to end any fight with just a single punch. You're never completely out of a fight because it can change with one well-placed fist.
Some MMA fighters have this ability and use it to great effect in their fights. They have provided wicked knockouts that will live on highlight reels for years.
Check out some UFC fighters with dynamite in their fists.