If I use Challenge in a showdown targeting my stunned 3 might unit against an attacking 6 might unit, does the stunned unit still deal damage via Challenge, allowing my other 3 might unit to finish off the damaged attacker?

Ruling: Yes, a stunned unit can deal damage through Challenge because Challenge damage is not combat damage, which is what Stun prevents. The stunned 3M unit deals 3 damage via Challenge to the 6M attacker, then the other 3M unit can finish it off in the showdown.

Sequence:

• Challenge is played targeting the stunned 3M unit and the 6M attacking unit
• Both units deal their might to each other (3 damage marked on the 6M unit)
• The stunned 3M unit dies
• The 6M unit (with 3 damage marked) trades with the other 3M unit in the showdown

Nuances:

• Stun only prevents combat damage, not damage from card effects like Challenge