In the very first episode, Grave wakes up and kicks ass not because he was "activated" by the doctor, but because he hears Mika screaming and he forces himself to fight before he's ready just so he can protect her. He then takes out what had been shown as near unstoppable monsters, and he wasn't even at full strength yet.
In the final episode , an extremely weakened and weaponless Grave taking out the Millenion swat team with only his bare hands and bricks. And he jumps good..
Actually, his bare hand. At the time of the finale, he was one-armed. He have already lost one of his arms after the fight against Bunji. This makes it more awesome when you see it.
Not only that but Brandon and Harry didn't kill the swat team members. They just shoot them in non-vital areas and just knocked them out.
In Overdose, after completing the labratory stage, Grave is confronted by Fangoram, whose Center Head gun actually dwarfs the power of Grave's handguns. Grave is shot by the Center Head and is left so injured his healing factor can't close his wounds properly. Juji and Billy manage to get Grave back to the Mika's truck for treatment, however, Mika reveals that she's been giving Grave her own blood, which has had serious effects on her health. Despite that, she's still willing to do a direct blood transfusion for Grave even though Spike says that's outright suicide. Juji and Billy try to hold her back from doing so and as Mika resists, Grave grabs her arm. Obviously in a lot of pain, Grave slowly rises up from his transfusion chair while Mika pleads with him to sit down and accept her blood. Grave ignores her and through sheer force of will, he triumphantly stands up, full of fighting spirit, much to the surprise and relief of everyone.
Spike: ...But how?! How could he get back up?!
Juji: A Deadman is just like anyone else...In the end...
Juji: ...It's only our strength of spirit that allows us to go on.
Rocketbilly (to Grave): Wow, you are amazing, man. You really are hands down the world's strongest Deadman.
(Grave stands there while Mika hugs his arm in relief)