I have some "badass" players in my group who do not fear death, 4 out of 6 to be precise, which causes problems for the rest players as they feel they are always getting dragged into trouble, trying not to break the group in two. When I say they do not fear death, even if I brought the whole pantheon down on earth vowed to wipe the party out, these 4 would still fight to death.
I am not trying to play favorites or punish the guys, so how do I cope with this problem? Which techniques should I use to make them value their characters' lives more, making the escape route seemingly a good alternative? Apparently I can't kill them, it would cause the whole party to go bankrupt, plus I hate the idea of paying a cleric and **poof** the character auto-magically is among the living once again. Moreover, they won't think twice before slaying a NPC who tried to mug them, or blackmail them. They bring no mercy on the table for the lives of NPCs (corrupted guards, bandits, massacring a small elf village which turned to the dark side), heading towards Lawful Neutral, but acting like Chaotics.
Partially, this is caused by my personality as a player, which may affect my viewpoint as DM. I always choose the supporting roles, which most times take the blame for the death of a party member, so generally I don't like the idea of killing. Maybe they know and take advantage of that, but if it is unavoidable I hold no qualms of killing them in order to keep them in check. But none have died yet, the worst that's happened is Two characters went down, but stabilised, the third one was lucky enough to get away with 1 HP on 3 attacks, no fudging.
Any alternative solutions/suggestions/ideas?
PS. We play DnD 4e, but that is irrelevant in my opinion.