Full pain is a term used when something hurts badly e.g. when two girls step onto your hand while you're having the time of your life at a staircase. Full pain is also an expression which describes a group of cool people.
ouch! she just stepped onto my hand. That really hurt :'(
boy: Look, there's a bunch of cool people over there!
girl: Yeah, I know that's full pain. I Wish I were as cool as them!