in bf1 attack hahs 1 unit with 5 might. Defence has a Shadow Clone and a Zed, Without a sound. What hahppens in the end of showdown?

The defender wins the combat. Both the attacker's 5-Might unit and Zed, Without a Sound are dealt lethal damage (5 each) and die during the Combat Cleanup; the 0-Might Shadow Clone survives untouched.

Sequence:

1. Combat damage (Rule 465): Attacker sums 5 Might, defender sums 5 (Zed 5 + Clone 0). The attacker must fully assign lethal before moving on, so they can only kill one defender unit (5 to Zed is the efficient play). The defender assigns 5 to the attacker's unit — lethal.
2. Combat Cleanup (Rule 466.1): Lethal-damage units are killed (attacker's unit and Zed). Units are then healed, and attackers are only recalled if defenders are still present — but the attacker's unit is already dead, so no recall.
3. Result (Rule 466.3): The Shadow Clone is the only unit remaining, so the defender is the only player with units → defender wins.
4. Control (Rule 466.5): The defender establishes control of the battlefield (clearing Contested), which is a Conquer if they haven't already scored that battlefield this turn.

Note: if the attacker instead split damage (e.g., 1 to the Clone, 4 to Zed), the Clone dies to lethal (1 damage ≥ 0 Might) but Zed survives with 4 damage — defender still wins. The attacker cannot kill both defender units with only 5 damage.