Well, I personally believe, that the greatest Darkness Dragon names, are the ones that go with the Element, such as: Shadow Spirit Mist NightShade and others.
Sorry if i repeat any answers Yami means darkness in Japanese yoru means evening in japanese kagayaku means shining in japanese onyx is a black stone onikisu is onyx in japanese minuit is midnight in french kuraku is dark in japanese maho is magic in japanese yonaka is midnight in japanese kanashimi is sorrow in japanese utsu is depression in japanese (i think?) akumu is nightmare in japanese sorry if i got some of the translations wrong. I tried at least! ;)