Does a creature with deathtouch and trample need to assign only 1 damage to each blocker before trampling over?

Normally, trample requires an attacker to assign "lethal damage" to each blocker before any excess can be assigned to the defending player (CR 702.19b). Lethal damage is defined as damage equal to a creature's toughness minus any damage already marked on it (CR 702.2b, 119.6).

Deathtouch changes what counts as lethal: any amount of damage dealt by a source with deathtouch is considered lethal damage (CR 702.2b). Because of this, assigning just 1 damage to a blocker satisfies the trample requirement of assigning lethal damage to that blocker, regardless of the blocker's toughness.

These two abilities combine so that an attacker with both deathtouch and trample only needs to assign 1 damage per blocker (or enough to reach their toughness if less than 1, but damage is always at least 0, so in practice 1 suffices). All remaining combat damage can be assigned to the defending player or planeswalker.

Example: Your 6/6 with deathtouch and trample attacks. Your opponent blocks with a 5/5. You assign 1 damage to the 5/5 (lethal due to deathtouch) and 5 damage to the defending player. The 5/5 dies, and your opponent takes 5 damage.

This interaction is explicitly supported by CR 702.19b, which states that the attacking player must assign lethal damage to blockers first, and CR 702.2b, which establishes that deathtouch makes any nonzero damage lethal.