The temptation is to call all skeletal warriors with full armour anna sword a "Death Knight" because, well, Death Knights are rather iconic. OK...
This chap had what it took, gorgeous plate armour, skull head, sword a bit short and stubby but clearly designed for serious brutality. Ironbreaker armour, washed in Nuln, cloak black DB with dark grey. The purple on the sword is intended to make it look a bit magical and radiant, but I'm not sure it worked. I might top it over with some blood red instead.
I was a bit pleased with the cloak at the back so here's a second picture.