If a character is Staggered, can he activate an Incidental (or an Out-of-Turn) effect?

A weapon with the Concussive quality can activate this effect with 2 advantages to inflict the Staggered condition for 1 round.

In one vs one this can be... a one way fight.

Shouldn't this effect be activated with 1 Triumph, like the Stunning Blow (Improved) talent?

Staggered just means you can't use any Actions with a Capital A. The target is still free to take Maneuvers or use Incidentals all they want.

And yes, in a one-on-one fight rendering your opponent Staggered, either by a weapon quality or a critical injury is going to give the attacker a huge advantage. But the other question is how often are weapons with the Concussive quality used in a one-on-one fight? And since you need to hit and score Advantage to trigger the weapon quality, there's always that chance you'll hit but not have enough Advantage to do trigger the Concussive quality, so it's not like it's a "sure thing."

And yes, in a one-on-one fight rendering your opponent Staggered, either by a weapon quality or a critical injury is going to give the attacker a huge advantage. But the other question is how often are weapons with the Concussive quality used in a one-on-one fight?

Force Pike with a Weighted Head attachment. That’s pretty deadly.

And since you need to hit and score Advantage to trigger the weapon quality, there's always that chance you'll hit but not have enough Advantage to do trigger the Concussive quality, so it's not like it's a "sure thing."

If you’re rolling enough dice, it may not be a mathematical "Sure Thing", but it is very highly probable that you will get what you’re looking for. From there, the combat can be a foregone conclusion.

And yes, in a one-on-one fight rendering your opponent Staggered, either by a weapon quality or a critical injury is going to give the attacker a huge advantage. But the other question is how often are weapons with the Concussive quality used in a one-on-one fight?

Force Pike with a Weighted Head attachment. That’s pretty deadly.

And since you need to hit and score Advantage to trigger the weapon quality, there's always that chance you'll hit but not have enough Advantage to do trigger the Concussive quality, so it's not like it's a "sure thing."

If you’re rolling enough dice, it may not be a mathematical "Sure Thing", but it is very highly probable that you will get what you’re looking for. From there, the combat can be a foregone conclusion.

If you're rolling that many dice against someone without enough ranks of Adversary and Defence to stop it, the fight was a foregone conclusion anyway.

Still, a Jury Rigged Superior melee weapon can activate the Concussive quality with only 1 Advantage and generates 1 Advantage at every attack. A good combatant (4 skill and 4 attribute) will stagger an Adversary 4 very easily.

Additionally Extra Boost dice (easy to gain from aim, support, etc...) greatly increase the number of Advantages generated.

I still think that the Consussive quality should be activated as the the Improved Stunning Blow talent: with 1 Triumph

Still, a Jury Rigged Superior melee weapon can activate the Concussive quality with only 1 Advantage and generates 1 Advantage at every attack. A good combatant (4 skill and 4 attribute) will stagger an Adversary 4 very easily.

Additionally Extra Boost dice (easy to gain from aim, support, etc...) greatly increase the number of Advantages generated.

I still think that the Consussive quality should be activated as the the Improved Stunning Blow talent: with 1 Triumph

Adversary 4 seems really excessive to me. In melee you'd have to roll against what, three Red dice? Even with four Yellow, I would call that a stout check. The odds are slightly in your favor, but I wouldn't bet the farm on it.

The trouble with activating Concussive with only a Triumph is you are comparing it to a talent that is argueably one of the more useless and overpriced talents in the CRB. But let's not do that debate again here.

All that to say, I think Concussive is fine as it. It can give an advantage in a one on one fight, but simply getting a good roll on Initiative will be a solid advantage too.

And how often are you going to have an opponent using a weapon with the Weighted Head attachment? Per RAW, the Force Pike actually doesn't qualify as it's not a bludgeoning weapon, and the description notes "are long metal poles tipped with sharp prongs that continually spark and buzz when active." (emphasis mine, taken from page 123 of FaD Beta). And there's been a noted shortage of Brawl or Melee weapons that quality and have enough hard points stock to allow the Weighted Head attachment in the first place? The Tinkerer talent only helps a little since it adds a single hard point, but as confirmed by the devs said talent is only once per item, with each rank having to be applied to a different item. Thus far, the only weapons that could qualify for the Weighted Head attachment and have enough hard points and aren't in the Force and Destiny Beta are the Shock Gloves (with Tinkerer), the Backhand Shock Gloves (Far Horizons), Drall Flashtick (Suns of Fortune), and the Riot Shield (Far Horizons, needs Tinkerer). FaDBeta adds the Refined Cortosis Gauntlets, Refined Cortosis Staff, and the Electrostaff, but the Weighted Head attachment isn't there, so for a group that opts to use just Force and Destiny and not use material from EotE or AoR, then said attachment can't be involved at all.

You've then got the simple fact that for many of the above weapons, they're vulnerable to being Sundered by an opponent using a lightsaber or vibroaxe, and it just takes 3 Advantage, a Triumph, or possibly even a Despair on the attacker's roll to have the Concussive weapon disarmed.

And as was also noted, if a PC with a Concussive weapon is going up against major NPC opponents that don't have at least 2 ranks in Adversary on a regular basis, then the GM hasn't done their homework.

There are weapons with a "native" Concussive effect (no need for an attachment), like the melee Thunderbolt Shock Prod (or the ranged heavy SWE/2 Sonic Rifle, but this has slow firing) both from Far Horizons .

An "expert" Gadgeteer (skill 4 and attribute 4) can have one such weapon with the superior quality (+1 advantage), jury rigged (to activate the Concussive 1 with 1 advantage) and with an attachment that give Accurate 2.

While aiming, this character has 75% to have at least 1 net success and 90% to have at least 0 net advantages (+1 from the superior quality) against an Adversary 4.

There are weapons with a "native" Concussive effect (no need for an attachment), like the melee Thunderbolt Shock Prod (or the ranged heavy SWE/2 Sonic Rifle, but this has slow firing) both from Far Horizons.

An "expert" Gadgeteer (skill 4 and attribute 4) can have one such weapon with the superior quality (+1 advantage), jury rigged (to activate the Concussive 1 with 1 advantage) and with an attachment that give Accurate 2.

While aiming, this character has 75% to have at least 1 net success and 90% to have at least 0 net advantages (+1 from the superior quality) against an Adversary 4.

1. If it's the GM throwing this against a player they should either not activate it cheesily every chance or simply not through that against a singular player.

2. If it's the reverse with the player weilding the weapon you have a slew of options as the GM. Firstly as the GM you control the world, that means the scenery, environmental effects, all NPC's including any who may be drawn to the scene so you only run into a situation you can't make challenging even if you want to if you're simply not trying that hard or are simply not well versed in your GM tools.

To start you don't always have to have the NPC's win or even be challenged all the time. Some times it's fun and empowering for a player to just get the chance to show off and be a badass.

Second you can manipulate the environment via what's occuring in the narrative or what you think would be interesting to throw extra setback at the player.

Third if the foe they're fighting has adversary don't forget despairs which can't be cancelled no matter what they roll. A single one of those could be the solution to your problem. Maybe they hit but he weapon slips from their grasp as it goes skidding across the ground several feet away, or worse yet the opponent manages to get a hold of it and even though he's staggered is about to turn the combo around on them. Maybe they hit something explosive nearby or the structural integrity of the floor gives out nearby and separates the player from the foe long enough for them to gain their wits back and call for help or pull out a ranged weapk and Fire back, etc etc