Deathtouch is defined in CR 702.2: any amount of damage a creature with deathtouch deals to another creature is sufficient to destroy it. The rule explicitly applies only to creatures, not to planeswalkers.
When a creature with deathtouch attacks a planeswalker (or redirects combat damage to one), the damage is converted to the removal of loyalty counters from that planeswalker (CR 306.7). Deathtouch has no interaction with this process; loyalty counters are simply removed equal to the damage dealt, and if the planeswalker reaches zero loyalty counters, it is put into the graveyard as a state-based action (CR 704.5i).
In short, deathtouch's destruction clause (CR 702.2b) never applies here because the damaged permanent is a planeswalker, not a creature. The damage still counts normally — it just doesn't carry the "any amount destroys" bonus.
Concrete example: Your 1/1 deathtouch Snake attacks your opponent's Jace, the Mind Sculptor (currently at 4 loyalty). Jace loses 1 loyalty counter and sits at 3 — Jace is not destroyed outright. If instead that Snake blocked a 1/1 creature, the creature would be destroyed by deathtouch even though it only took 1 damage.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.