I created a little sub-system called Doom that I've used in several Savage Worlds games.

The basic idea is that everyone is Doomed. All PCs start with a Doom of 1.

At any time, the player can choose to invoke Doom. When the player invokes Doom, their PC's action succeeds in the most spectacular way possible (e.g. the dragon is slain, or the dark lord is thrown into the Abyss where his soul is destroyed forever, or the chief necromancer is killed in a magical explosion). The player gets to describe their enemy's death scene and how their PC wins awesomely.

Then the player has to roll to see if their PC survives. The player rolls a single d6, no re-rolls, the result is taken as-is.

For a Doom of 1, a roll of a 6 means the PC has met his doom and dies, again in the most spectacular way possible (e.g. The dragon blood sprays poisonous death on the PC, or the dark lord drags the PC into the Abyss with him where both their souls are destroyed forever, or the magical explosion consumes the chief necromancer and the PC). I usually let the player describe that, too, and sometimes add a bit of input.

EDIT: I would simplify the roll by using roll over Doom rating to survive.

If the player rolls 1-5, the PC survives his Doom...for now. The PC's Doom increases by 1 (e.g. Doom becomes 2) and his survival range decreases by 1 (e.g. Next time the PC uses Doom, he dies on a 5-6).

Everytime a PC uses a Doom point and survives, Doom increases by 1 and the survival range decreases by 1 (e.g. For a Doom of 3, death occurs on a 4-6, for Doom 4, it's 3-6, for Doom 5, it's 2-6, and Doom 6, it's automatic).

The best thing about this mechanic is the player never has to use it if they don't want to. It's all their choice.

But if the player makes that decision to use Doom, it's on them: they get a really big win, defeating the Big Bad in a spectacular way, which may be enough of an incentive to some players to have their PC court death.

I've had players state emphatically "Nope! Never gonna use that! Are you crazy?"

And I've had more than a few use it. Three players in one encounter used their Doom. Two had Doom 1 and the third, after I explained how Doom worked, demanded Doom 3. They defeated the assembled Big Bads and then, one after another, solemnly rolled their d6s. The two PCs with Doom 1 both rolled a 6 while the Doom 3 player rolled a 1!

None of them complained about the outcome, after all, they chose to use it.

So with Doom, players get agency to do awesome things but can still have their PC die from a single die roll.

And when I use Doom in a game, I pull all other random Deaths off the table and just leave Doom.