im not sure but i think he can decide how much damage he wants to cause to anything that is about 10m radius around him. so his power only works in a short distance
do you guys remember the first chapters there was this voice and that voice was counting numbers from his hatred those numbers are probably the damage increasing so right now his attack power is 9999 so thats probably his hatred increasing the damage that he inflict on his enemies (this is what i think his powers is)
Yup his power is to convert all his negative emotions into fixed damage.
So those he doesn't hate don't take damage and those he consider enemy take damage as soon as they are in his range.
I'm confused about what kind of power does he have? He's way too OP to the point of this manga being boring.