I don't doubt your translation (or Japanese speaking skills), but could you have got it wrong? I only suggest this because Yu Yu Hakusho had a "Dark Tournament" saga in the anime. I'm just wondering if that may be what you mean.
Maybe you are right however, and this is completely unreleated.
Tau's right on the money. They translated it differently, because the Japanese could mean something naughty.
é”界統一トーナメント literally says "The Unified Hell Tournament". é”ç•Œ can also be "Spirit Realm", "Underworld", or "Demon Realm". It's really up to you, it's basically hell.
So that would make é”界統一æ¦è¡“会 "The Unified Hell Martial Arts Tournament". Or something like that.
But if you must, you can call it the "Dark Tournament". But I personally wouldn't. I'd find a cooler way to say it (and one that sounds less Engrishy than my translations, XD)
~DS