________ is a deeply underappreciated villian.

[DrNewGod]

Validus. This one of the scariest figures in all DC lore. Enormous. Kryptonian-level strong. Solar Flare Quality Brian Bolts. Nightmare Ugly.

He should be a marquee DC bad guy.

[Riv86672]

Baron Bedlam could’ve should’ve been DC’s answer to Zemo.

[Multiverse]

Ma'alefa'ak, NUFF SAID!!!

[married guy]

Shadow Thief!
Guy should scare the **** outta anyone who meets him.
(Marc Andreyko's take in Manhunter is a personal favourite)

[Android 17]

The Ventriloquist. James Gunn needs to cast Steve Buscemi and finally have the character and Mr Scarface make the jump to a live action movie already.

[K7P5V]

Prometheus would definitely be my choice. Just give him a dependable jockstrap, and he'd be unbeatable (XD)

[caj]

Psycho Pirate

[JT221]

Hugo Strange.

[K7P5V]

Pre-Crisis Killer Croc, especially the Gerry Conway version. Pretty darn, near close to being a criminal mastermind (IMHO):

[Sutekh]

Gimmicky villains with insanely good gimmicks, like Angle Man or Chronos or Mirror Master. Dimension-warping or time-travel powers or shunting people into 'mirror-space' (or calling out an evil reflection duplicate!) can do all sorts of funky stuff. "Oh, you're invulnerable? Good luck getting out of this other dimension I've just sent you to..."

But also villains with utterly insane defenses, nearly untouchable under most circumstances, like Shadow Thief or Gentleman Ghost. Imagine how they could terrorize a hero unable to effectively fight them?

[j9ac9k]

I say this every time this thread pops up:
Evil Star - dude can destroy a planet. And his little Starlings are a fun, creepy visual that just amps up his threat level.

[Johnny Thunders!]

Terra Man, always Terra Man, and Anton Arcane!

[Twice-named]

I always thought Victor Zsasz had potential to be a truly terrifying character.

[DrNewGod]

The Ventriloquist. James Gunn needs to cast Steve Buscemi and finally have the character and Mr Scarface make the jump to a live action movie already.

IMO, the Ventriloquist/Scarface was the greatest Bat-villain to emerge after Ras al Ghul. Just, genius.

[DrNewGod]

Gimmicky villains with insanely good gimmicks, like Angle Man or Chronos or Mirror Master. Dimension-warping or time-travel powers or shunting people into 'mirror-space' (or calling out an evil reflection duplicate!) can do all sorts of funky stuff. "Oh, you're invulnerable? Good luck getting out of this other dimension I've just sent you to..."

But also villains with utterly insane defenses, nearly untouchable under most circumstances, like Shadow Thief or Gentleman Ghost. Imagine how they could terrorize a hero unable to effectively fight them?

I particularly like The Gentleman Ghost when whether he's genuinely supernatural or an amazingly gifted grifter is ambiguous.