So Kath's ability reads:

When attacking, the defender receives 1 stress token if he cancels at least 1 result.

What happens with Gunner?

I cancel a crit in the original attack and gunner kicks in. I cancel another crit from Gunner do I get 2 stress tokens or 1 as they are separate attacks?

(this is assuming I target both attacks on the same ship)

I cancel another crit from Gunner do I get 2 stress tokens or 1 as they are separate attacks?

I'd say one, because it says at least 1 [crit] result, so it's a on/off type thing. If you cancel 1 or 5 you get 1 stress token.

I would agree with one, but Gunner is a separate attack, so I was wondering.

Now if I attack two separate targets, then they both take stress, which is clear.

It is two separate attacks, thus generating up to two stress tokens.

Particularly valuable with Marksmanship, as that will work with both attacks (unlike a Focus, which only works with one).

Also of note, the Gunner's attack doesn't necessarily have to shoot at the ship you shot at.

My understanding is that the defender would end up with two stress tokens because they are two attacks. My basis for this is order of operations.

1) Attack.

2) Defender cancels a crit and the attack misses.

3) Defender cancelled a crit during an attack and takes a stress.

4) Gunner activates

5) Attack 2

6) Defender cancels a crit (attack may or may not miss)

7) Defender cancelled a crit during an attack and takes a stress

These are two wholly separate and independant attacks.

Separate attacks, so any abilities which trigger off an attack have the opportunity to do so twice. If the target cancels a crit on each attack, they'll get two stress tokens.

I like the 2 tokens theory much better and the rules specifically call out Gunner as a separate attack, supporting the theory.

Considering who all disagreed with me, I think I'll change my answer to two.

The fact that they are separate attacks does make sense that it would cause two stress.

Of important note: Double Stress means that it takes two turns of green maneuvers to clear, making this a nasty thing to do to someone when you're running Ion Cannons as well.