Does reducing a creature's toughness to zero with a -1/-1 counter count as lethal damage for state-based actions?

State-based actions check two distinct conditions that can destroy a creature. The first is having damage marked on it equal to or greater than its toughness (CR 704.5g). The second — the relevant one here — is simply having toughness 0 or less (CR 704.5f). These are separate triggers and operate independently.

When a -1/-1 counter reduces a creature's toughness to 0 or less, the game destroys it via CR 704.5f, not because of 'lethal damage.' No damage is involved at all. The creature doesn't need to have any damage marked on it; the toughness value itself being 0 or less is sufficient.

This distinction matters practically: effects that prevent lethal damage or replace destruction 'from damage' (like regeneration or indestructible in some older phrasings) do NOT save a creature killed this way. Indestructible does still protect against 704.5f, because that SBA uses the word 'destroyed' (CR 704.5f), and indestructible prevents destruction (CR 702.12b). But a damage-prevention effect alone would not help.

Concrete example: You control a 1/1 Soldier. Your opponent puts two -1/-1 counters on it with Devoted Druid's ability, making it a -1/-1. At the next state-based action check, the game sees its toughness is -1 (less than 0) and destroys it under CR 704.5f — not because it took lethal damage, but because its toughness is 0 or less.