i loved the water sample puzzle! LOL as a kid i had NO IDEA WHAT THE HELL I HAD TO DO but i found out how to solve it now, it's so easy.
without using infinite ammo:
hardest? most likely very hard/ nightmare/ lone wolf/ whatever else in outbreak.
out of 4, 5 and 6, 6 is the hardest on no hope. there are a lot of ways for enemies to kill you, and you can't stock up on ammo/ gold eggs/ fas as well as you can in 5, etc.
3 on hard wasn't too difficult for me. loved playing it on hard because of the mine thrower, eagle and custom shotgun. easy was just way too easy, imo.
out of tank controls, i think remake was the hardest, even on easy. too much to do, a lot of back tracking, etc. it is also the game i played the least (besides a few scenarios in the outbreaks), so i don't always remember what to do or where to go.
i don't think code veronica had a difficulty setting.. at least not on the ps2?
The Nintendo 64 version of Resident Evil 2 had Nightmare mode, it also had a random item arangement mode were herbs and ammo are all switched around randomly which made the game more interesting.that was such an epic mode.
Code Veronica on my first try. I had no idea how busted the knife was in that game. And it is the only RE game that caused me to restart the entire game because I didn't have enough ammo to fight the Tyrant on the plane.
Very anti-newbie. There was no way I would think to store the empty fire extinguisher for Chris' Magnum Revolver end game if I had not read some tips beforehand.
Many bosses had OHKO moves. Alexia 1 with her touch of death (although very easy to keep your distance), Nosferatu could instantly knock you over as soon as the battle began, if you didn't move away enough. Tyrant could knock you over in seconds if you did not move in time in Battle Game.
To a lesser extent, Bandersnatch groups could stunlock you to death as they play volleyball with your head.
A devious end game trap could ruin a flawless run for having a hiccup.
RE 0-Hard Mode no contest. That mode forces you to hoard items/ammo and avoid enemies as supplies go so quickly and you can run out of ammo at essentially any time. RE Remake Hard mode is second, followed by RE 2 Nightmare difficulty (PC version only).
When facing a zombie apocalypse, don't join up with a group. Why? Because you'll end up blowing your own head off due to all the pointless drama caused within.
There are some poor gameplay choices that make the game needlessly hard. Like mentioned, Bandersnatchers can put you in stun lock, especially if there are two. Poison Hunters are a pain. Puzzle solving and navigation can be difficult because you don't have any knowledge before hand that you will be playing as Chris and those are his puzzles. I can't tell you how long I was stuck at a certain section because I was looking for something that allowed Claire to get a tank for the diorama. But it is for Chris only.
On a personal note, the game is also very dark. It was mainly my TV setttings, but I didn't realize it until later. This caused me to miss ammo on top on not knowing the knife was too good.
I went for RE1 advance mode, being Chris just makes matters even worse. on Advance mode 2-3 hits and your dead, The Hunters are the worst, if they hit you once your on red caution, which then means the hunter has a chance to instant kill you. However for some strange reason the Zombie critical hit rate is much higher on advance mode so your popping heads left right and center.
You are talking about Directors Cut correct? Advance mode gives you the Silver Handgun which has the chance for a headshot. IIRC you cannot score headshots with the regular (Black) handgun.
On topic I would have to agree that RE1 Advance mode is the hardest. Those Hunters are downright brutal.