Does the attacking player get another action after the defender plays an action card, if the attacker had already passed their initial action?

Ruling: Yes, the attacking player gets another action after the defender's action resolves. Focus passes back and forth between players, and passing focus automatically when a chain resolves is different from voluntarily choosing to pass focus.

Sequence:

• Attacker has focus and passes without playing anything
• Defender has focus and plays an action card
• Attacker can react with reaction-speed cards (optional)
• Defender's action resolves and attacker automatically receives focus
• Attacker can now play an action card (like Cleave)
• This continues until both players consecutively pass focus without playing anything

Nuances:

• You can only play one action at a time, but action-speed cards can effectively be used to "react" to opponent plays by waiting for focus to return
• If a chain resolves and kills a unit (like Kai'sa), you still gain focus and could play Cleave, but not on the dead unit
• Passing focus automatically when a chain resolves does NOT count as voluntarily passing focus for the purpose of ending the showdown
• Both players must consecutively pass focus without playing anything for the showdown to end