If an enemy uses Falling Star on a unit with 3 might but has Guardian Angel, how does it work? Does the first one trigger GA and the second kill, or does it do 6 and GA?

When an enemy uses Falling Star on a unit with 3 Might equipped with Guardian Angel, the interaction is determined by the fact that Guardian Angel acts as a replacement effect for the "die" event.

Here is how the sequence unfolds:

The Sequence

1. Playing Falling Star: Your opponent plays the spell, targeting your unit with both instances of 3 damage. The spell is placed on the chain.
2. Resolution: The spell resolves, dealing 3 damage, then another 3 damage (total 6 damage).
3. Applying Damage:
   • Because your unit takes lethal damage (6 damage to a 3 Might unit), it would normally die.
   • Guardian Angel triggers as a replacement effect at the moment the unit would die. It replaces the "death" event with: kill the Guardian Angel, heal the unit, exhaust the unit, and recall the unit to its controller's base.

The Result

• The unit survives: The death event was prevented and replaced. The unit is healed and moved to your base.
• Guardian Angel is destroyed: Only one instance of the effect is needed to replace the single "death" event.
• The unit does not "die twice": The second instance of 3 damage does not kill the unit again because the unit is already safe, healed, and recalled to your base, and the "death" event was already replaced.

According to RiftJudge FAQ #9721 and Rule 373, replacement effects replace the event that would have happened. Since the unit's death was replaced by the gear's effect, it never actually dies, meaning there is no second "death" for the unit to undergo.

This is my interpretation based on the mechanics of replacement effects (Rule 373) and the provided FAQs. No official rule states the damage happens as two distinct "death" events; the damage is simply dealt, and the replacement effect handles the outcome of the unit reaching lethal damage.