So... 3 Binayre Pirates goes into a bar with big bad Bossk...

Anyway, the story is rather not interesting, in the end they put 3 harpoons on the same target and Bossk pushes through another crit result. I am wondering what happens now?

Notice that there is no "OR" between the effects but they are triggered at different phases of the attack, hence cannot happen together. Moreover if the target was destroyed by the

Lets look at three different scenarios - target is U-wing. First 3 Harpoons pushed no crits thanks to Guidance Chips (you can change the crit to hit as well!). Now, scenarios:

1. Initially U-Wing lost 4 shields. Bossk pushes 1 crit, but it is not a Direct Hit. Each other ship at range 1 suffers 3 damage in total and the U-Wing get 3 facedown damage cards. As I read Then discard this card and receive 1 facedown damage card. - you deal 1 damage and discard one card at the same time, hence you will not do the splash damage on the second condition when the 3rd card is dealt because you already discarded all 3 condition cards.

2. Initially U-Wing lost 4 shields. Bossk pushes through 3 damage total, including an uncancelled critical. At this moment the U-wing is not yet destroyed. Now, we need to resolve each Harpoon: 1st will do crit splash and facedown to U-wing. But the U-wing is not yet destroyed hence you go to 2nd and 3rd critical splashes of harpoons, U-wing gets another 2 facedown damage cards, discards all harpoons and is destroyed. The same happens if Bossk did 4 damage with crit (would kill U-wing but first splashes would clear all the condition cards) or if Bossk did 4 damage without a crit (U-wing is destroyed and hence deals 3 splash damage upon destruction but that is not .

3. Initially U-wing lost 4 shields. Bossk used his own Harpoon and dealt 4 damage including uncancelled Critical hit. Due to the critical splashes, all ships in range 1 suffer 3 damage in total. Additional, in step 10 (Remove Destroyed ships) the new Harpoon is resolved and another 1 damage is dealt to ships in range 1. Or it should be considered as the same trigger (assigning new Harpoon if this attack hits assign condition card and when you are hit by an attack)? Then it would be up to the initiative on whether this Harpoon is dealing damage sooner or later but in the end the effect stay the same - all 4 harpooned cards resolve altogether. Interesting for using scavenger cranes on all...

In the end it looks like there is no option to deal 6 damage by splashing harpoons (unless you use 6 harpoons) because although the wording seems unfortunate it still resolves in only 1 of 2 steps of combat. Did I miss something? Is there any other interesting mechanic to use those harpoons with?

It remains to be seen and FAQed. Personally I'm expecting Harpooned to be binary in nature - each ship being either Harpooned or not, and it n stacking at all.

I'm a little more worried by how easy it is to push that crit through for scum on a cost budget (with scavenger cranes no less!) over the other 2 factions and how easily several current meta lists can intergrate it without much sacrifice. (Ps10 aces might be a blessing for imps into that sort of thing though).

As for the harpoon that kills a target. My gut says thats the janky wording on applying the condition, applying after the attack is fully resovled means it cant be applied to the already removed ship hence no splash damage

the condition card is not unique or limited (as labeled) so afaik you can get multiple harpooned!