Darkwave is a genre that is rarely ever "pure", in that there's almost always overlap with other genres. Usually the overlap occurs with dark synth, gothic, postp-unk, and gothic rock, but there are also plenty of occasions of overlap with industrial even. Emphasis is on the beautiful darkness.
Check out these artists who specialize in this style of music.
Feel free to recommend some artists not included in here (these artists specialize in it) in the comments section (for an eventual best of countdown).