There is no legitimate Dark Pikachu that can be caught in game, it can only be obtained through ROM hacking. However, shadow pokemon exist in Pokemon Colosseum (but that's not dark).
i guess 100% of hp
The Shadow Pikachu card has 999 HP.
You don't need to give it to pikachu, you select "use" and it should show pikachu's hp bar. select pikachu and it will evolve into raichu! hope this helps.
300 hp
275 HP, CONCOURS HAS 300 HP
Well, here are their base stats: Pichu HP: 20 Attack: 40 Defense: 15 Sp. Attack: 35 Sp. Defense: 35 Speed: 60 Total: 205 Pikachu HP: 35 Attack: 55 Defense: 30 Sp. Attack: 50 Sp. Defense: 40 Speed: 90 Total: 300 Raichu HP: 60 Attack: 90 Defense: 55 Sp. Attack: 90 Sp. Defense: 80 Speed: 100 Total: 475 I would pick Raichu, but you have to remember that once you evolve your Pikachu into Raichu, it won't learn any more moves by leveling up. I leveled my Pikachu to level 41 so it would learn Thunder, then I evolved it. Pikachu learns Light Screen at level 50 if that interests you.
the dark star core regains all of its hp so be carefull
Although water type Pokemon are weak to electricity, Feraligator's strength and stamina would help it win against Pikachu. What are you saying man. If pikachu uses a strong electric move feraligatr will almost be out of hp and die. So the answer is pikachu.
300
Shadow Lugia does.
300-350
300 HP