Part 10: Episode 10: ReptaEpisode 10: Repta
We finally get to kill the other really annoying support character: Repta. He carries a gun that can one shot us even at totally full health and will not hesitate to use it in that capacity. Luckily, I avoid most of the attempts to do so, but still, you'll see that if you hesitate for even a second when the fight starts you could get wiped out totally.
The Repta fight is sort of schizophrenic at times. I had to trash a recording of the last hour of the game due to audio and video issues where I attempted to show off that fighting him on his level would get you killed, but then I beat him. In celebration I slid off some level geometry and died in the pit below the fight. Then I had to fight him again as the checkpoint isn't for another room. You can also take a step back from where the game puts you after the intro scene for Repta and be relatively sheltered and kill him from there, but you won't be able to do anything as the platform directly in front of you falls away. The railings in the fight have weird hitboxes as well, they seem to be at least twice as large as they should be and can make fighting Repta difficult when you get snagged on one while trying to escape him.
Like Quill, headshots with the rail gun are the best option here. I screwed myself over by not reloading it before I picked up all the ammo and ended up three rounds shy of where I could have been. Barring rail gun ammo, precision rifle bullets do enough damage to be useful. Bosses are incredibly resistant in this game, anything short of the rail gun is nearly useless and it should be your first option every time. The fact that they can often kill you in one shot while you have to perfectly line up multiple shots is part of the difficulty of the game from what I can tell.