And Nathan can't be beat. Sure, knockout gas and tranqs will work on him, but when I say unbreakable skin, that's a vague way of saying indestructible. Not only is his epidermis impossible to break, but his organs, bones, even his blood is invincible.
Also, an attribute to this is an extremely capable immune system. Most bacteria and viruses won't affect him, and sleeping agents I mentioned earlier won't affect him for long.
Alongside his indestructible form, is his immense power. He has an extremely high stamina, and his power is immense. He can punch a planet into oblivion without breaking a sweat.
And just to add insult to injury, he's extremely intelligent, and observant. The reason Jack so easily disabled him is due to his worry for the others.
He has flaws, of course. Because of his pacifist nature, he wouldn't dare hurt a fly, and spends more of his time caring over others. This can be used against him to someone's advantage.
Nathan may be very intelligent, but he is not immune to common manipulation and mind control.
Now you know why I made him a pacifist.