Superhardcore 2K is a straight-up hardcore survival server with deathban, no restarts, and a pretty unforgiving setup overall. The spawn radius is 1000, the world border is 2000, and there is no built spawn, so you are dropped into a harsh survival world from the start.
Enhanced mobs make things even rougher, and hacks or mods are bannable. This is meant to be a real survival challenge, so join ready because you do not get another chance.
The server is Distant Horizons compatible, runs Dynmap for a live web map, and offers an optional resource pack with a custom soundtrack tied to important or rare achievements. If you want a hardcore world with a bit of extra atmosphere and a survival guide available through this is the kind of place to jump into.