How does Yasuo's Remorseful ability work in combat, specifically: Does Yasuo survive when killing a larger defender? Does this happen before showdown? Can players use action/reaction spells in response?

Ruling: Yasuo's ability deals damage to the target without receiving damage back. This occurs during the initial chain of combat showdown (when all "when I attack/defend" abilities trigger), and both players can play reactions during this chain just like any other chain.

Sequence:

• Yasuo's attack ability triggers on the initial combat showdown chain
• The ability resolves and deals damage to the target unit
• Yasuo does not receive damage from this ability
• Players can use action and reaction spells during this chain
• After the chain resolves, combat continues normally

Nuances:

• If Yasuo has Mask of Foresight, you control the order abilities go on the chain, so you can make Mask resolve first to add to Yasuo's damage
• When attacking a unit with Deflect (like Qiyana), you can decline to pay the deflect cost for Yasuo's triggered ability, but if you decline, the ability will fail to finalize