I'm not sure how terrifying you want your foes to be, but while I was modding a race to be fun to play with as a an adventurer I decided to make them have a civilization and such, but initially they were female only. Later I figured out how to make fully differentiated sexes and didn't realize that a bunch of steel angels and their much less common hyperfast non-winged steel mini-armoks would, well, run armok during world-gen and take over (though they are naturally very peaceful) until I limited their site pops and such heavily. They still do a good job setting up weird little mountain hamlets and towns, but that isn't the point here.
The point is, I've made adventurers into master vampires from the dark ages mod, had them geared with full sets of artifact gear using a modded metal (steel mass+candy properties), legendary out the ass combat skills, using the silly-fun "bullet time" speed boost ability so they're running around at 9.9 speed right?
I had one of these adventurers who I had a lot of fun playing with after I found you can hit someone with a platinum war hammer in the head, send them flying, and THEN cut their head off with a battle axe in mid-air... she has something stupid like 1300 kills. She rampaged through hell but the demons were boring, she's killed hydras by trying to rip their guts out with her teeth and having them BLEED to death (I then realized the guts were way too heavy to rip out like that... ) and singlehandedly depopulated the world of monsters and beasts besides the few FB's hiding from her in the caverns.
There is one thing I will not do with her: pick a fight with a steel angel, nothing is more terrifying in adventurer mode than something which is just as brokenly fast as you, has no organs to injure, no bones or skin to feel pain from, has hand-to-hand attacks tuned and designed for removing limbs AND can fly.
I'd love to help out and test some modded creatures for you folks by putting it up against an angel-blender, by which I mean taking control of in adventurer mode and picking a fight with some... though I don't recommend going with the full speed-boosted solid steel delimbing machines themselves, having something which can last against them at all is a good judge of how much fun it would be to fight it with an army of decked out military dorfs.
Oh, if you would like a solution to the "voidspawn won't use weapons" problem, I've got a lot of practice tweaking hand-to-hand attacks for delimbing, as I said, there are some values that you can set to what seem rather absurd levels which do the job very well.