Here is my ultimate darkness deck. It's completely focused on devastating an opponent with powerful dark cards.
Monsters
Mist Archfiend
Diabolos, King of the Abyss
Doomcailber Knight
Dark Grepher
Armageddon Knight
Dark Armed Dragon
Doomsday Horror
Fear From the Dark
Archfiend Soldier
Phantom of Chaos
Battle Fader
Dark Hunter
Regenerating Mummy
Yubel
Yubel - Terror Incarnate
Yubel -The Ultimate Nightmare
Hannibal Necromancer
Darkness Neosphere
Dark Blade
The Supremacy Sun
Dark Crusader
Prometheus, King of the Shadows
Trageodia
Card Guard
Rainbow Dark Dragon
Double Coston
Necroface
Plague Wolf
Spell Cards
Monster Reborn
The Beginning of the End
Allure of Darkness
Recurring Nightmare
Fires of Doomsday
Heavy Storm
Spell Shattering Arrow
Veil of Darkness
Dark Core
Tribute to the Doomed
Dark Hole
Mystic Plasma Zone
Dark Eruption
Lightning Vortex
Trap Cards
Dark Illusion
Dark Spirit of the Silent
Hate Buster
Eradicator Epidemic Virus
Deck Devastation Virus
Escape From the Dark Dimension
Bottomless Trap Hole
Zoma the Spirit
Darklight
Nightmare Wheel
Mirror Force