When a character succeeds an strike and they spend 2 opportunity to cause a critical strike, is it in addition to the normal Fatigue caused by the attack, or instead of it?

If an attack causes both Fatigue and a critical, and the Fatigue gets over the top, does it also cause a second critical wound?

Yes to all.

Opportunities always happen before the success resolution of a roll and in addition to it (unless they state otherwise, I suppose). The clearest example of this are any of the range-extending opportunities, which make the success of the action possible in the first place.

So, it is possible to get two critical wounds from the same strike? It seems a little... wow, isn't it?

1 hour ago, Sedda said:

So, it is possible to get two critical wounds from the same strike?

Yes. Three, even, with the right Kata.

Generally speaking, being hit by swords is detrimental to one's health.

That's by using Veiled Menace Style, by the way, on an incapacitated and (disoriented or unaware) target and spending at least three opportunities on a successful Strike.

2 Opp to Crit, 1+ Opp to Crit from VMS, and then extra Fatigue becomes a third Crit.
Since they are incapacitated, the first crit will make them Unconscious and increase the severity of crits 2 and 3 by 10.

It's not easy to achieve, but that person will be in very bad shape.

2 hours ago, Harzerkatze said:

Yes. Three, even, with the right Kata.

Generally speaking, being hit by swords is detrimental to one's health.

T'is only a flesh wound.

On 4/29/2020 at 10:32 PM, Sedda said:

If an attack causes both Fatigue and a critical, and the Fatigue gets over the top, does it also cause a second critical wound?

Just to note: if you're on, say, 9/10 fatigue and take 3 fatigue, you don't suffer a critical strike.

You suffer a critical strike if already on 11+ fatigue and are hit again.

Oh, I misread that rule, thanks!