Tonight I snagged and played a few new custom maps, here's some "Hell on Earth" difficulty highlights and descriptions of each:
KF-Milltown-Burgerking
That should be Burger TANK. This is an adaptation of the final showdown in the "Hard Rain" campaign for Killing floor 2. It's a medium-small map with lots of clutter to get caught up in if you aren't careful, but if you know the map well, you can use it to your advantage.
KF-playboy_clean_edition
A map consisting of a long, straight causeway with no cover other than other zeds. I discovered partway into it there's a button to play a custom meme-tastic soundtrack at EXCRUCIATINGLY LOUD LEVELS so some of this highlight got muted for copyright.
KF-outrun
Well, it ain't KF-SynthwaveThing, but it's got the aesthetic. What it really is is a TINY map with lots of scenery consisting of a single short length of street with practically no cover (unless you count hiding behind a street light cover). Very challenging.
KF-TankaichiBudokai
Yyyyep, it's a Dragonball Z themed level. Quite large and expansive, with lots of cover to hide behind. Also it has the "cars zooming down the street" gag from the Gas Station Arcade level that kills most anything it hits, so be careful crossing the street (and if you're clever you can get zeds to die getting run over). Really, this level largely trivializes the game's difficulty, even on Hell On Earth. Purely a gimmick level.
KF-UT-FacingWorlds-Classic-2004_Gravity
An excellently done port of the best level from Unreal Tournament, Facing Worlds. There are two versions, a normal one and this one, which features the most popular UT mutator to use on this level, low gravity. The low gravity, admittedly, does make it a lot easier to escape the zeds, but it also makes it much more dangerous to get hit by something that knocks back because it can easily send you flying off the edge for an instant death. A great trip down memory lane for old school FPS gamers.