Personally, if I was going to run a high adventure, high action game with highly competent characters taking on crazy risks, experiencing dramatic setbacks but likely to find some way to come out on top, I'd be inclined to use something based on Blades in the Dark It's perfect for it.
But if you're after something more traditional (and, based on your mention of hit points, I'm assuming you're working on something at least vaguely d20ish, my first instinct would be to include an "escape clause" rule.
At a certain point, if things are going badly, the PCs get a chance to withdraw/escape. If they choose to do so at that point, they may suffer injuries and setbacks, but they will survive to fight another day. On the other hand, if they're unwilling to accept defeat, shit just got real, and PC death is now on the table. No punches pulled, dice in the open, you could be dead at any moment.