Deathtouch is defined in CR 702.2: any amount of damage a source with deathtouch deals to a creature is enough to destroy that creature. The key word is creature. Planeswalkers are not creatures (unless something has made them so), so the deathtouch ability has no special effect when damage is dealt to a planeswalker.
When a creature with deathtouch deals combat damage to a planeswalker, that damage is still redirected (via CR 306.7) and reduces the planeswalker's loyalty counters normally. However, the planeswalker does not get destroyed from a single point of damage — it is only removed from the battlefield when it has zero or fewer loyalty counters (CR 306.9).
The deathtouch replacement effect only triggers the 'destroy' condition through the state-based action in CR 704.5h, which explicitly checks for creatures, not planeswalkers. There is no equivalent state-based action that destroys a planeswalker due to deathtouch.
Example: Your 1/1 creature with deathtouch attacks and your opponent blocks with nothing, so you redirect the damage to their 5-loyalty planeswalker. The planeswalker loses 1 loyalty counter and now sits at 4 loyalty — it is NOT destroyed, because deathtouch does not apply to planeswalkers.
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.