Don't forget that Psycho and Slasher can stack!
Roger, that. Results: Add Bloddy Moss, and 3 ranks of Abominable got the Big Lizard down to 60 HP. Adding Psycho did the job, went straight down to -50 HP. I wasn't sure how low they displayed the negative HP, so I added slasher, and it looks like -50 is as far down as they go. So it is easily possible to kill a 500 HP Barney the Dinosaur with a reasonable energy weapons build and a modded laser rifle. That's, of course, assuming you didn't remove that redonkulous sneak attack X2 damage multiplier like I did by mod.
-Gunny out.