Resident Evil 3 allows you to choose from three progressively more difficult options when you first start playing. Assisted, which is a bit easier, Standard, which is how the game is balanced to provide a decent challenge to the majority of players, and Hardcore, for people who love a good challenge.
It also has two other difficulty modes that you can unlock, Nightmare and Inferno.
To unlock Inferno mode, you need to beat the game on Nightmare mode. It’s a daily basic chain of progression; you need to prove you can beat a difficult mode to unlock an even more difficult mode. It doesn’t matter what rank you get; you just need to make it through the game.
Nightmare mode is a solid step up in difficulty from Hardcore, but Inferno mode is something else entirely. Autosave is disabled, there are fewer typewriters and item boxes, and enemies will pretty much one-shot you. Item locations will all be switched around as well, and getting an S Rank will be incredibly difficult.
In short, Inferno mode is the ultimate test for Resident Evil fans who are looking for a challenge.