Most I've gotten is seven damage with a range one shot from Maarek Stele on Bossk. Rolled one hit, one eyeball, and one blank, and added the crit from ATC. Used Calculation to turn my eyeball into a crit, and Palpatine to turn the blank into the crit. The Hound's Tooth only had one shield left, and it blanked on its single dice roll. Used Stele's ability to get a triple Direct Hit in for a total of 7.

I've one shot a firespray, I think that's probably the single most amount of damage i've ever dealt.

7 Die advanced proton torpedo (Opportunist + Jan ors, ) ended up with 4 hits 3 crits, - all three were direct hits. the firespray blanked out.

At that point, is someone allowed to blame luck without having to listen to diatribes against it?

Yes and no, I think I rolled 2 crits, a hit and an eyeball and three misses Etahn converted a crit, atp converted 3 blanks to focus. Atp are ruthless! The real luck was 3x direct hits.

Not sure if it's the most damage I ever did, but I recently one-shotted Corran Horn with a Proton Rocket from Tycho: 5 hit vs 3 blank. I felt bad because it happened really soon in the game... but then again, it's Corran so he deserved it... and he should have focused...

Suhlak Cluster deals 6 hits and a critical without any evades on a Y-wing, he's probably the gimmickiest I'll go to roll lots of reds.