Kaioken is really hard to maintain, I just got it recently but I'm thinking of getting rid of it the drainage is so much more worse compared to SSJ. SSJ is a free skill with no SP needed sure it has a large cooldown but all you have to do is collect the 7 dragonballs and you get a free boost where as Kaio its 1-3 of your valuable SP.
Don't forget that Kaioken at lvl2 already gives bigger attack boost than SSJ. At lvl3 it drain as much as SSJ, majin buffed and with healers ep buff at tmq its np
Yea, and it depends of your style. If PvE is your way, max it. I have it maxed on Turtle and lvl1 on Swordman. And it's not hard to fit KoK 3/3 at Fighter's build.
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