Does assigning 0 damage to a blocker with deathtouch still count as lethal damage?

When a creature with deathtouch deals combat damage to a creature, any amount of damage — even 1 — is considered lethal (CR 702.2b, 702.2c). However, 0 damage is not 'any amount of damage'; it is no damage at all. A creature must actually be dealt damage for deathtouch to apply.

During the combat damage assignment step, an attacking creature with deathtouch must still follow the rules of CR 510.1: it must assign at least lethal damage to each blocking creature before assigning any damage to the next. Critically, 'lethal damage' for a deathtouch creature means assigning at least 1 damage to each blocker in sequence (since 1 is enough to be lethal via deathtouch), not 0.

So if you assign 0 damage to a blocker, that assignment is illegal unless that blocker is being 'skipped' under the trample rules — and even then, you can only skip to the next blocker after assigning lethal damage (at least 1, given deathtouch) to the current one. You cannot assign 0 to a blocker and claim deathtouch makes it lethal.

Example: Your 3/3 deathtouch creature is blocked by a 5/5 and a 2/2. You must assign at least 1 damage to the 5/5 first (lethal due to deathtouch), then you can assign the remaining 2 damage to the 2/2. You cannot assign 0 to the 5/5 and put all 3 on the 2/2.

Reference rules: CR 510.1 (combat damage assignment), CR 702.2b–702.2c (deathtouch), and CR 119.2 (dealing 0 damage is the same as dealing no damage).