It didn't hurt him it momentarily stunned him and he would've killed him had Kenobi not magically blew him up.
Malak can hack him up and he'll regenerate, he can freeze him but his lightsaber can't really penetrate his armor, and hand to hand he has reflexes that keep up with Kenobi who is faster than amped Malak.
I'm not seeing Malak being able to destroy him unless he knows the Kamehameha wave