Does Dark One's Blessing apply if the character doesn't stay at 0 HP?

[holywhippet]

Warlock's with the fiend pact get some temp HP if they reduce a hostile creature to 0 HP. Some monsters and classes have abilities to avoid staying down eg. zombies can make a saving throw to avoid staying down unless they took radiant damage or a critical hit. Generally this means that they drop to 1 HP instead of 0. Does Dark One's Blessing still apply in these cases?

[Arkhios]

Warlock's with the fiend pact get some temp HP if they reduce a hostile creature to 0 HP. Some monsters and classes have abilities to avoid staying down eg. zombies can make a saving throw to avoid staying down unless they took radiant damage or a critical hit. Generally this means that they drop to 1 HP instead of 0. Does Dark One's Blessing still apply in these cases?

As soon as the trigger occurs, you get the described benefit for that event. I'd say that it counts, because you did reduce the creature to 0 HP. Whatever triggers for the creature afterwards is irrelevant.

To rephrase:

Reducing the HP to 0 is the trigger for Dark One's Blessing to grant you THP.
Reducing the HP to 0 is the trigger for a X to occur to the monster.

In both cases, the effect occurs immediately after the triggering event, and unless either one specifically prevents the other, they both happen simultaneously.

...At least that's how interpret it, and would rule at my table.

[nickl_2000]

Sure, are you planning on keeping a troll around that you can beat down to 0 HP with your second attack every round?

[Laserlight]

Depends on the phrasing of the monster's ability. If it's "when you would drop to zero, you instead...", then I would not say that gets the blessing.