Just from experience Night Lords benefit insanely well from Berzerkers with the Axe/Chainsword combo.
I run a death star of a Dark Apostle, Exhalted Champion and 8 Zerkers, kitted for CC in transport. That's a 3+ hit, reroll, 3 Attacks per mini at x2 +1 S and AP modifiers and a bonus attack, add to that a reroll to wound and two fight phases you always put the pain on.
I've yet to encounter something that can survive it and at a reasonable points cost it's a mainstay of my armies now. With Night Lord traits it's glorious to rush them in, murder a significant amount, impose a penalty and have the rest run away.
Otherwise Slaaneesh marines, Icon, Chain Axes and DTFE can really hurt enemy units, even after turn 2 - basically getting a psuedo-charge can really make the difference.
Remember that as Unaligned, Night Lords have no mechanical reason to not pick a variety of marks & icons, unless fluff is your game.
"Ambition is the biggest killer of Momentum"
Starting afresh with my Chaos Space Marines.
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Project Rebuild, Reboot, Recycle:
Stripping, rebuilding and remaking my Guard army.