ΔE 13.5, fair: the same colour family, but not a straight swap. Outlining Black is noticeably darker, more muted than The Darkness.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Outlining Black is noticeably darker, more muted than The Darkness.
The same difference applies the other way round: The Darkness is noticeably lighter, more saturated.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See The Darkness on the colour wheel See Outlining Black on the colour wheel
All matches: The Darkness equivalents · Outlining Black equivalents