Permafrost!It's not megabeast-high (it's got a fair amount of semimegabeasts, they play nice), since that fucks with civs,
BUT!1. Lots of necromancers.
2. Lots of goblins.
3. Dead dwarves. Almost always.
4. Diddly squat for metal.
5. Easy access to evil glaciers.
It may take a few tries to get a suitable world: necromancers destroy things a lot easier in v47, so you may be in tough luck if your humans don't want to survive world gen (or exist in the first place, or make necro towers, or all that jazz), and also you may not find a reanimating/thralling biome first try, since the world is pretty small. I think the seeds in there should give a pretty solid world, just be sure to turn them off of random. It's the best I can get without modding. Well, worst. If you'd like the authentic Permafrost experience, I suggest embarking somewhere with an aquifer, with only a copper nugget and an anvil. I can probably whip up a DFhack script for turning light aquifers into heavy aquifers (there's one that turns heavy to light, so it's only a line or two I'd need to change), though I think tiletypes should let you just create aquifers.
EDIT: Okay, so the terrain seed is fine, but you'll want to change the history seed: everything in the world dies just around year 100 from necromancers. Use the terrain seed, since it's annoying when the plains end up too small and get evil-ified, preventing humans, which also prevents necromancers. And then stop world gen when it gets somewhere that looks satisfactory, since I've got it set to 10k years currently.
Oh right. Do
not ask why it is version 6.2 of Permafrost.