No! Kidney punch is an illegal punch in most combat sports like Mixed Martial Arts and boxing. You’re not allowed to intentionally strike the lower back of your opponent. The referee will give you a warning when he notices such a punching technique in a professional boxing match. If a fighter or a boxer repeats such illegal activity, he may be penalized or disqualified. In most cases, if it is unintentional and your opponent can continue the fight, you may be pardoned by the referee and escape a point deduction. In a situation where you’re only trying to hit a fighter at his core, and he turns and gets hit on his kidney area, you will likely escape punishment and as it wasn’t an intentional kidney punch.