Does deathtouch work with trample to kill a blocker with 1 damage and trample the rest?

Normally, a creature with trample must assign "lethal damage" to each blocker before it can assign any damage to the defending player or planeswalker (CR 702.19b). "Lethal damage" is defined as damage equal to the blocker's toughness minus any damage already marked on it (CR 702.19b references CR 119.6).

Deathtouch changes what counts as lethal. CR 702.2b states that any nonzero amount of damage from a source with deathtouch is considered lethal damage. This directly interacts with the trample rule: because even 1 damage from a deathtouch source is lethal, the attacking creature only needs to assign 1 damage to each blocker to satisfy trample's requirement, and the rest may be assigned to the defending player or planeswalker.

This interaction is explicitly confirmed in CR 702.19b: "When a creature with deathtouch and trample is blocked, the attacking player assigns damage considering the deathtouch rules for determining lethal damage."

Example: Your 6/6 creature has both trample and deathtouch. Your opponent blocks with a 5/5. You only need to assign 1 damage to the 5/5 (lethal due to deathtouch), and you can assign the remaining 5 damage to your opponent. The 5/5 will be destroyed, and your opponent takes 5 damage.

This is one of the most powerful keyword combinations in the game, as it makes even modest power attackers very difficult to chump-block effectively.