I know it is possible and i did the main setup in radiant. I made a trigger_multiple that kills the player once he falls in a specific place. Gave it the targetname horrific_death.  However, when on quick revive solo or in co-op, players will go on last stand. How can i make it so players that fall there die permanently?

Remove quick revive then kill them.

Thanks J! I'll try that. But, what happens with playing Co-op? Players will go on last stand...

Thanks J! I'll try that. But, what happens with playing Co-op? Players will go on last stand...

You would have to chance the bleed out timer to 0 when they touch the trigger.