There's one in the original Guild Wars that has your exact same character build. I believe they altered it later, but at one point it was possible to murder it by playing a Necromancer and taking a ton of curse skills with your Curse stat set to 0. Curse skills tended to come with fairly serious penalties, and if you built it right the penalties could do more damage to your Doppelganger than the skills did to you. Sit back and watch it kill itself, awesome fun.