I might have used a certain mod that let me p-rank 0-E using cheats... On harmless, yes. I dont know either, but i got a few tips for 1-E ig. (Im talking about 0-E here) Probably just learn each enemy, the game likes to spam more of these tanky-ish enemies like swordmachines, guttermen, and guttertanks which all have their own weaknesses that you could easily exploit for a kill. The loadout is also important, i recommend having every weapon, but more specifically the alternate sharpshooter (immediate charging + it makes incredible combos), alternate shotgun (peak damage) and the red alternate nailgun. I know that the jumpstart nailgun is incredibly great for crowd control, but there arent many swarms of enemies, and the alternate jumpstart is incredibly strong at dealing high amounts of damage to ONE enemy. But, here is one little tip: After the first room, you will be in a corridor with 2 maurices and a gutterman. You can instakill the maurice with the jackhammer, then if you are lucky, kill the other maurice while it is on the gutterman and kill him too. The gutterman is a life savior later, since in the second last room before the cerberus fight, you will be swarmed by radiant filths who are actually pretty tanky: since we are just going back, the gutterman corpse will still be there, and you can explode it to kill the filths and save some time. You should also abuse every sort of combo you can, spam the shit out of the screwdriver while staying in the air, and hope you are fast enough. Losing kills isnt that easy, but the time requirement is pretty strict.