The kaioken is an upsurge of energy enhancing your speed, strength, ki, ect. for only an instant in the anime of Dragon Ball Z. If it’s added into the mod, then maybe it should be about 5 seconds. It should raise your stats in a tab maybe saiyan-ing (saying) Special Stats, and it raises your BP. For it to be fair, I think all races, Namekian, Human, Saiyan, Half Saiyan, Acrosian, ect. should all be able to use it. It would be hard to achieve it so maybe make an “if” statement in the code, (sorry not trying to tell you how to program, plus I am only beginning so that statement could be wrong) so if your stats are a specific level they can be increased in the Special Stats tab. I hope you take this into consideration because it’s a big but minor and not very known attack in the anime and to early DBZ fans.