When Yasuo attacks and triggers his ability, does he kill the defending Yasuo before combat damage, or do they deal damage to each other and both die?

Ruling: The attacking Yasuo's ability triggers and kills the defending Yasuo before they deal combat damage to each other.

Sequence:

• Yasuo attacks
• Yasuo's ability triggers
• The defending Yasuo is killed by the trigger
• No combat damage is dealt between them

Nuances:

• Combat still technically occurs (relevant for cards that care about winning combats), but no combat damage is exchanged in this scenario