Mr. Satan here!! Man, have I got news for you!! I've got word on which
  Darkness Poke'mon are good and which Darkness Poke'mon are bad. I'll check
  them out right now!!
  Neo: Genesis:
  Murkrow- Mean Look might cost a Darkness Energy
  but it prevents retreating while you relentlessly beat away at the adversary
  with Feint Attack, which always hits no matter what. So, Mean Look + Feint
  Attack is an evil combo!! This is indeed one of Neo: Genesis's best cards.
   
  Sneasel- Fury Swipes is nothing new. Sure, it
  could do up to 30 damage on the first turn, but flipping coins?? It serves as
  a step attack only. Whereas Beat Up, while also requiring coin flipping, is
  gonna be good. It could do up to 120 damage on turn 2 if you flip enough
  heads, but hey, all you need are about 4-6 heads to make it really count. This
  is also one of Neo: Genesis's best cards.
   
  Neo Promos:
  Murkrow- Peck is nothing new, it's the same
  pitiful attack that was on Spearow. Whereas, Pursuit is gonna be good. It
  will always do 30-40 damage when you use it for the first time and with the
  adversary having the risk of 10 damage after taking 30-40 when they retreat,
  believe me, that's gonna hurt!!
   
  Neo 2:
  Houndour(D)-
  Translation:
  Basic Poke'mon
       Houndour    
  40 HP  D
  C: Bite  10
  DC: Thief  20
  Before doing damage, discard all Trainer cards
  attached to the Defending Poke'mon.
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
      Bite is just weak, but Thief,
  if you can get 2 Darkness Energy on, is gonna be powerful if your environment
  is heavy on Defenders and Poke'mon Tools. Unfortunately, you have to put up
  with 40 HP to get it. Thief is nice when you evolve into Houndoom and play
  Recall, but this is probably your worst choice in Darkness Poke'mon. Better
  evolve quickly.
   
  Houndoom-
  Translation:
  Stage 1: Evolves from Houndour
             
  Houndoom         70 HP  D
  DCC: Crunch  30
  During your opponent's next turn and your next
  turn, when the Defending Poke'mon takes damage, that damage is increased by
  20(after applying Weakness and Resistance).
  RRC: Flamethrower  50
  Discard 1 R Energy card attached to Houndoom in
  order to use this attack.
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
      Crunch is always gonna do
  between 40 and 60 damage depending on the number of Darkness Energy you attach
  and it's gonna hurt like crazy. Flamethrower is nothing new, but on this
  Poke'mon, it could do at least 60 if you attach your Darkness Energy. Very
  broken card.
   
  Umbreon-
  Translation:
  Stage 1: Evolves from Eevee
           
  Umbreon          80 HP  D
  CC: Tackle  20
  DDC: Feint Attack
  Choose 1 of your opponent's Poke'mon and this
  attack does 30 damage to it(don't apply Weakness, Resistance, Poke'mon Powers,
  or other effects).
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
         Tackle is
  nothing new and Feint Attack is a very accurate move but without Mean Look to
  back it up and Feint Attack's cost, it's gonna be difficult to use. I wouldn't
  count on this guy being very useful at all.
   
  Tyranitar-
  Translation:
  Stage 2: Evolves from Pupitar
             
  Tyranitar            
  80 HP  D
  CCC: Slam 30x
  Flip 2 coins.  This attack does 30 damage
  times the number of heads.
  DDCC: Darkness Fall  50
  Flip a coin for each Poke'mon on each player's
  Bench. This attack does 30 damage to that Poke'mon for each heads. (Don't
  apply Weakness or Resistance for Benched Poke'mon).
  Weakness: None  Resistance: P -30 
  Retreat Cost: CCC
   
        Slam is nothing
  new, but Darkness Fall is definitely something. It will KO any Haymaker
  Poke'mon in one move and (sigh) bash both Benches. Your opponent will not be
  likely to survive the onslaught after you attack, but neither will you. I'd
  use Transparent Walls if I were you. He's definitely not the best, but he's
  okay. Unfortunately, his Basic form Larvitar is severely weak and his Stage 1
  form Pupitar is excessively reliant on luck to be effective.
   
  Neo 2 Promos:
  Umbreon-
  Translation:
  Stage 1: Evolves from Eevee
           
  Umbreon         70 HP  D
  CC: Quick Attack  10+
  Flip a coin. If heads, this attack does 10 damage
  plus 20 more damage. If tails, this attack does 10 damage.
  DDC: Pursuit  30
  If the Defending Poke'mon retreats during your
  opponent's next turn, Umbreon attacks the Defending Poke'mon for 10
  damage(apply Weakness and Resistance).
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
        Quick Attack is
  nothing new, but Pursuit is just evil. It's always gonna do between 50 and 60
  damage, and the possibility of 10 damage upon retreating, oh, man!! Absolutely
  evil!!
   
  Neo 3:
  Houndoom-
  Translation:
  Stage 1: Evolves from Houndour
              
  Houndoom        70 HP  D
  R: Dying Flame  20
  Discard 1 R Energy card attached to Houndoom in
  order to use this attack. Take 1 D Energy card from your discard pile and
  attach it to Houndoom.
  DCC: Darkness Attack  30+
  Flip a coin for each D Energy card attached to
  Houndoom. This attack does 30 damage plus 10 more damage for each heads.
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
       Dying Flame is
  powerful(20 for one) and strategically useful even though you dump an R Energy
  card to use it. Darkness Attack is just deadly. It's always gonna do 40-60
  damage, and if you flip coins and flip heads, you could do up to 110
  damage(WOW!!). This card gives people reason to play 4 D Energy in their deck.
  Still, you better have Ecogym.
   
  Murkrow-
  Translation:
  Basic Poke'mon
     Murkrow        
  40 HP  D
  C: Call for Family
  Search your deck for a Basic Poke'mon named
  Murkrow and put it onto your Bench. Shuffle your deck afterward.(You can't use
  this attack if your Bench is full).
  DC: Flock Attack  10+
  Flip a coin for each Murkrow in play(including
  this one). This attack does 10 damage plus 10 more damage for each heads.
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
      Call for Family is
  strategically good and Flock Attack is cool since it'll always do from 20-30
  damage added onto the number of heads you flip. He could do at most 90 damage
  on turn 4. Unfortunately, he has low HP. He's not great but he's good.
   
  Neo 3 Promos:
  Sneasel-
  Translation:
  Basic Poke'mon
      Sneasel   50 HP 
  D
  D: Thief
  Discard all Trainer cards attached to the
  Defending Poke'mon.
  CC: Quick Attack  10+
  Flip a coin. If heads, this attack does 10 damage
  plus 20 more damage. If tails, this attack does 10 damage.
  Weakness: None  Resistance: P -30 
  Retreat Cost: C
   
         Thief is cool
  but it doesn't do damage and Quick Attack is too old school. Not your best bet
  for a Darkness Poke'mon.
   
      Best Darkness Poke'mon:
  Houndoom(Neo 2)
   
  Worst Darkness Poke'mon:
  Umbreon(Neo 2)
   
  Ciao for now!
  -Later,
       Mr. Satan