>>713991891In Ps1 original he shows up at scripted moments (although there’s way more and a bunch of mutually exclusive depending on how you’ve progressed) but the key difference is that in Ps1 game when he shows up nothing else changes, you still have to complete whatever objective you were doing, just now Nemisis is after you while you do it. You can run from him until he leaves (but doing this causes surprise spawns in a ton of possible locations) or you can fight him, which is extremely difficult but gives rewards.
Remake when he appears the only objective you have is “run forwards along linear path” there’s one tiny section at beginning where you can technically go find some collectibles while he’s chasing you, and technically fight him, but you shoudve already grabbed those collectible anyway, and they are super optional even if you didn’t, and by “fight Nemisis” I mean throw a singke grenade at him. It’s also possible to have proper fight, but why the fuck would you when a singke grenade does same job as all your bullets? And after that first encounter every future Nemisis encounter is either a scripted “run forwards through hallway with nothing else to do” or a boss fight where you have no choice to fight him.