Jason

So can you just start ng+ and warp to The Nameless King in Dark Souls 3? No. If your goal in your second playthrough is to just beeline through the game, there is a pretty linear path available. If you just want to re fight Melania, you're obviously going to have to get to her. What is NG+ for in your mind? Playing through the game again is my answer. If you're just looking for a boss rush there are probably mods available but that's not something available in the base game for any FromSoftware title.

"The Blackgaol Knight has few major resistances not granted by high armor and is particularly not resistant to any Status Effects. Go in with a Bleed, Frostbite, or Scarlet Rot build to make short work of this." Is definitely immune to bleed, frostbite and rot (I assume all status but I specifically tried those). If he's not immune he's resistant enough to make no difference (like Melania vs scarlet rot lvls) Just walking sideways vs the crossbow barrage works you don't even have to run. Aside from that being dialed into his weapon art and follow up attack is the main issue. Carian piercer was a lesson he never seemed to learn if you want to borderline cheese it.