Okay, I was playing a bit in the lab vs. Deathstroke to test low gunshot nerf.
Thanks to the nerf you can now reversal punish Deathstroke's Low Shots on block with From The Deep (DB2), almost anywhere short of 100% full screen (think Raven range).
But my advice to you guys, even the people better than me at Aquaman? DON'T TRY IT, lol.
The reason why I think you shouldn't even try to punish this move with reversal DB2 is that that shit is MUCH harder than the CPU set to reversal mode makes it look. As a human, getting that punish without messing up is EXTREMELY hard to do. I would honestly compare it to a Super Turbo reversal, it's THAT hard.
The reasons it's so difficult to punish:
(1) LGS does not jail. If you release low block or hit an attack button before blocking the 2nd hit (both of which can naturally happen buffering a reversal), you will get hit and DS gets frame advantage.
(2) LGS inflicts extremely little blockstun (which, obviously, is why it doesn't jail). You have a VERY short window during the 2nd shot block to buffer a reversal before you lose that window. And of course even if you were blocking straight down, you STILL have to go back to neutral, THEN start your command, whether you're using default or alternate controls. Unless you're playing on a Hitbox-like controller where going through neutral is VERY fast and easy (and risks NO other inputs from a finger/hand slip), this is VERY hard to do QUICKLY and without messing up.
This means that unless you are an absolute MACHINE, typically one of two things happens trying to blow up LGS with Aquaman's DB2:
(1) You do it too early and you get hit by the 2nd gunshot. Not a lot of damage, but DS gets frame advantage and a free second gun afterwards to push you back.
(2) You do it too late and DS blocks DB2. DS has a MUCH easier time punishing Aquaman DB2 than Aquaman does punishing LGS, so against any DS with a brain, you'll typically eat a Quick Guns punish followed by chip+pushback from a free gun afterwards.
But the good news is, of course, that you don't need this extremely hard punish to beat Deathstroke in the first place. Guns are annoying, but solid blocking and a cautious approach will eventually get you into mid-close range where you have a LOT more tools to control Deathstroke, and he has to take big risks to kick you out. Honestly if anything this matchup has always been in Aquaman's favor, as long as you play patiently and pay attention to what zoning approaches the DS player favors. Does he like to check your feet with low guns? keep you from jumping with air guns? Does he intentionally do nothing to provoke you to dash or jump on cue? Will he jump at you with jump 3 if you creep into a certain range? Can you get to a range where you can provoke him to try and anti-air you with Sword Flip, and then bait and punish it?
Anyway, moral of this story is, don't be a hero vs. Deathstroke. You don't need to be in order to win.