[@FalloutJack][@Double]

What fallout said about making them inverse of buffs is basically what I was going to do. Think of it like this...

A buff of 2.5 is actually 1 + 1.5x
So a debuff should also be 1 + 1.5x , but in a different way

But the problem here lies in, "how does something this powerful effect the user? How do they pay for using it? Does it come out of one of their stats? Or..."

I think the best way for this is to introduce the concept of paying for an attack straight out of your ki. So if you have a power level of 100. And use 50 for this debuff attack, you would be debuffing your opponent by 125. And you're not going to be able to put that 50 points toward your other three stats. So in other words, your debuff is based of how much power you put toward your move, not your opponent's base stat that is being effected. 

This in mind, I would like to change something regarding exhaustion calculation. From now on, secret techniques cost double what you pay to use them. So when you're using a secret technique against someone who hasn't seen it, you'll be getting a great deal on exhaustion cost. (Example: 50x2.5=125, but it will only cost 10 to exhaustion) You'll be getting a fair deal on a times 2 boost (example: 50x2=100, and the cost will be 10) But you will be running inefficiently if you use the 1.5 bonus (example: 50x1.5=75, but again, you will be paying 10 to use it.) Why then, would you ever need to use a 1.5 boost if it's inefficient? Well, as inefficient as it may be, it could still provide just enough boost or debuff to win you the match. 

I know that sounds like a lot, but does that make sense. I hope I didn't overcomplicate my explanation.