Pain is one thing. You mind and body being toyed with as he sees fit. That's another thing. Broken bone here jabs at slopy form there. He is training you to be the best. He doesn't care if you fall on the ground. You fall you die. You run out of energy you die. You make a mistake... Yeah as I said he can be a ass when training people.
But after a few sessions with him. Well normal people won't be able to keep up with you. And considering most of the targets I have in mind for this rp for quite a while. You need his training to have the reaction time to not get slaughtered. I'm not saying you will all be made into one being army's but you will be much better off.