What if?

Greedo A is firing at Greedo B... then Greedo B can interupt to perform attack but then Greedo A can interupt to perform an attack... then Greedo B can....

WHAT?? How to resolve this loop?

The game loops infinitely, so it's a draw.

Seriously though, the answer is probably either:

A) Slow on the Draw only triggers once per each figure during this nonsense.

B) "Perform an attack" is different from "Declare an attack", and so the original Greedo that started this never gets a chance to utilize the other Greedo's Slow on the Draw ability.

B has some weird implications for other abilities/command cards and I'm pretty sure this doesn't make sense. It would also invalidate Jyn's command card. So I suspect that isn't right.

My guess is A.

An ability can only be triggered once per timining instance.

In this case, the timing instance is the first attack. During this first attack, each Greedo can trigger his "Slow to Draw" ability once. So a total of 3 attacks will be resolved if both players chose to resolve it and no figure dies before the 3rd attack (the original one) is resolved.

In a 4 player game, this can cause up to 5 attacks (if each greedo targets a greedo of a previously not involved player).

/edit: The previous sentence is incorrect. The attacker has to attack Greedo, no chaining possible.

But more than 3 attacks are not possible if I understand the rules right.

It's not exactly in the rules, but the interpretation (confirmed with FFG) is that Slow On the Draw triggers only once (per side) in such an attack.

There's a discussion about it somewhere here.

One found, but this is not the one:

https://community.fantasyflightgames.com/topic/219752-slow-to-draw-parting-shot/

B) "Perform an attack" is different from "Declare an attack", and so the original Greedo that started this never gets a chance to utilize the other Greedo's Slow on the Draw ability.

Every attack contains the declare target step, which is also declaring an attack. Declaring an attack is a shorthand for that declare step of an attack. Slow on the Draw requires that you know the target of an attack, which is not known before that step. But both Slow on the Draws trigger only once. (Perhaps another time if the other Greedo gets to perform Parting Shot instead of his originally declared attack.)

In a 4 player game, this can cause up to 5 attacks (if each greedo targets a greedo of a previously not involved player).

You wouldn't be able to change targets like this - it would be limited to 2 Greedos firing at each other. The target of the attack has to select the Greedo that declared the attack as the target of its attack.

The attack from Slow on the Draw has to target the attacking Greedo with the ability, but a Parting Shot can target any figure.

I'm too lazy right now to figure out how many attacks that could make at maximum in a 4-player skirmish (if we assume you can and want to attack a figure that has already suffered damage upto their Health).

In a 4 player game, this can cause up to 5 attacks (if each greedo targets a greedo of a previously not involved player).

You wouldn't be able to change targets like this - it would be limited to 2 Greedos firing at each other. The target of the attack has to select the Greedo that declared the attack as the target of its attack.

You are correct. I was a bit brain dead when writing that comment. Only 3 attacks possible in total. I'll edit my previous post to reflect that.