One

Ikken hissatsu is often referred to in Karate. It translates as one strike finish.

It means to target vital areas, and to hit with sufficient force to debilitate an opponent.

I just read a long-winded argument on the internet about how great/stupid it is. Neither side seemed to understand what it means.

Karate people seem to have an "attack". Watch them fight, and they really don't move all that much. Not a lot of jabbing, or picking at the opponent. They stand, they move slowly, and then without warning they explode.

Speed goes from zero to sixty. Several techniques are thrown as the fighter propels himself forward. Each attack is thrown with full power and speed and with very bad intentions.

Several of the attacks hit. The kick to the chest strikes like a cannonball. The opponent's head is snapped back by the force of a blow. The punch to the ribs buckles the target's legs.

Almost before it has begun, the Karateka is out of range again.

So how is this a one-attack finish? Simple. Each of the separate parts of the attack were thrown with enough speed and power to do meaningful damage. If a jab-like attack is used, it is delivered like what a boxer would call a "heavy" jab; meant to snap the head back sharply and cause disorientation. Major attacks are meant to do a hell of a lot more damage than that.

It is also a one-attack finish in that the attack was a single entity consisting of multiple parts. It was all one attack, and meant to finish the fight. Each of the parts was an attack in its own right and had the potential to incapacitate the target by itself.

Tournament Karate does not always follow this model, but often does. It is a game. Karate self-defense is very focused on the concept of ikken hissatsu

Does Ikken hissatsu mean we only throw one attack? Don't be silly. I have been in Karate for 30 years, and my first Sensei already taught the concept the way I've described.

It means to attack suddenly, strike very hard, hit precise targets, use several attacks, and get the hell out of the way again.

Cuz you never know.