I'll be straight with you, mate — Basalt is hard to dupe well. It's a deep, soft near-black with a green-grey undertone that stops it reading as flat coal, and that's exactly the bit cheaper paints struggle to copy.
The nearest match in our database is Dulux Black (LRV 1.2), but it lands at ΔE 7.8 from the original. To put that in context: under ΔE 1 is imperceptible, under ΔE 2.5 is very close, and 7.8 is a difference you'll clearly see side by side. Dulux Black is genuinely blacker and lacks Basalt's warm green-grey lift, so it'll feel harder and more clinical on the wall.
The other contenders drift further still. Crown Rebel (LRV 4.1) comes in at ΔE 12.7, and COAT David Rose (also LRV 4.1) at ΔE 11.2 — both noticeably off. David Rose is a lovely colour in its own right, but it's not standing in for Basalt.
So here's my honest take: none of these are true dupes. If you specifically want Basalt's character, the real Little Greene tin is the right call. Their Intelligent and Absolute Matt finishes are excellent, and on a deep shade like this the pigment quality earns its keep — you'll get cleaner coverage and a richer depth than a budget black.
But if the brief is really "I just want a great soft near-black and I'm not wedded to Basalt exactly," then Dulux Black is your best-value option from this list — solid paint, widely available, easy to top up.
Practical tip: whichever black you choose, prime first with a grey or tinted undercoat rather than brilliant white. Deep colours over white can need three or four coats to bury the brightness, and a darkened primer cuts that to two. Always sample a big patch and live with it across a full day — blacks shift dramatically between daylight and lamplight.