I initially guessed 50%
health was considered "low health." If you were to melee attack light enemies (i.e., non-heavy enemies like most Bullymongs) at 50%
, it would cause them to stagger. Though after experimenting, this doesn't seem to be the case.
Based on my observations, I'd say "low health" is ~33% health (or 1/3 health).
Fortunately, it is pretty clear when the ability was applied in a kill. Normally you deal a fixed amount of damage to everyone. When the ability is applied, you see a boost in the damage dealt and you get a nice "buzz" sound and a slashing animation for every hit.
To test this, I respec'ed Zero and went off to fight making sure I didn't level up any more during the tests. As a baseline, I fought off enemies with only the Deception skill and no other skills. Every melee attack I dealt gave 55
damage.
I saved and restarted to go on another run. This time I added Killing Blow Level 1 to the mix. Again, most hits dealt 55
damage. Using a weak gun, I chipped enemies' health to around 50%
(as close as I can get it) and hit them with a melee attacks. Still did 55
damage. I then tried for 25%
. Again, as best as I can, I chipped them down to as close as I can to 25%
then hit them with a melee attack. I got boosted damage and other indicators of a successful hit. So it's definitely applied at least at 25%
.
However I noticed that at times when I wasn't quite at 25%
but a little higher, I was still able to get the successful hit. So apparently it was higher. After a few more tests, I came to the conclusion that it is at 33%
at max.
To see if the level of the skill affects this, I tried again with Killing Blow Level 2 and up. You get even more damage of course but it still seemed to apply at 33%
and didn't change.
Best Answer
Laser Sight skill improves accuracy of Sabre Turret's shots - how clustered the shots are. The Sabre still rotates pretty slow.
As the turret is more useful as a damage sponge than as a damage dealer (in late game), it is generally deployed at enemies' feet, so the accuracy boost is unnecessary. But the skill also grants the turret a visible laser beam, so one skill point would give you a nice indication of what the turret is thinking :)
I've tried to take screenshots of actual spread, but haven't thought of a place to stage an experiment. Shooting range is small, and the turret is already pretty accurate to nail most targets it bothers to acquire. Anyone can think of a good place, let me know.