I understand what you mean but his lack of beatability is kinda what cripples him as something to genuinely be afraid of or intimidated by, at least in my view. As you pointed out, part of what made Nemesis so intimidating was the risk vs. reward factor of going against him: you could just try to avoid him and hope that he'll eventually go away or you'd avoid getting fucked too badly by him, or you could take him head-on, remove him temporarily as an immediate threat, and even get a health item out of it. With Mr. X it's just all risk, no reward: he's never gonna die, you're not gonna get anything out of beating him, and at worst he's gonna just force you to take the most roundabout routs to achieve your objectives, and he won't ever go away until you accomplish them. Not saying it was a bad concept, just that I feel it was implemented poorly in the game.