I might be able to shed some light here. See, I generally DM in a way that generally appeals to players like your friend. I’m going to try and explain my reasoning and it might help you understand what he’s looking for.
In my games, the PCs generally succeed in their broad aims. We play to find out, not if they can, but how they do it, and what does it cost them. Character death is rare, and if I can help it, it’s never due to a single missed roll. Players get the opportunity to adjust their plans, sneak out when they are obviously outmatched, and are able to make miraculous escapes in the nick of time. When things go really wrong, are knocked unconscious and left for dead, or are captured. (If you are wondering how to run this, look at fate points in wfrp 2e, the idea is you give them a negative consequence and take them out of the fight instead of killing them outright).
This does not mean characters never die. A campaign that doesn’t end without a pc sacrificing themselves for the greater good is boring, but this makes it a conscious choice of the player.
This does not mean the PCs can just fail their way to success. They get plenty of opportunity to figure out a strategy that gives them the upper hand, to out-talk, out-plan, out-number or out-think foes too powerful to take on head on. But if they are dead set on doing it the stupid way, and I am satisfied I have provided enough information telegraphing the way it will end, then yeah, TPK away.