Just be sure to max the Runner perk. The end boss is next to impossible without it:( You're not right
There are a lot of usefull perks which can help you to kill The Prison Keeper. The most usefull perks for it are:
Bonus Warden, Energy Weapons Master, Runner, Repair drone, FastLoader, Sharpshooter, Sniper, TheChosenOne, Weapon Focus on Railgun
2ValKaze. These are your locuts :) My locuts are stronger and has another AI ))))
2Effulgent: Thank you for your response! There are 32 types of enemies and it's already to late to tweak them all... But I take it into account in further games
 "Waterfalls 2"){kind=icon}
 "Blosics 2"){kind=icon}
 "Space Death Worm"){kind=icon}
 "We are all birds"){kind=icon}
 "Mecharon"){kind=icon}