Actually when the JLA teleported the General on an asteroid, they don't care if teleporting him in a place like that would mean he would possibly die, maybe cause of a meteorite or a comet hitting him or a star going supernova, or something like that, but the General like Doomsday was a threat to the mankind.
he killed Zod and his two minions with Kryptonite thats when he took the solemn vow never to kill ever again.even that debacle with Doomsday he still really wasnt trying to kill him.
the stupidest thing ive seen superman do is save the cyborg. the cyborg trapped him and another little alien guy on a ship, they fought supes won but when the space ship was blowing up with the cyborg he was all like "nooo, i know he's my enemy but i cant just leave him to die!!" and went back to save him... i swear he can be such a dumb ass at times