ΔE 20.4, loose: different enough that you should pick on purpose. Intermediate Green is noticeably lighter, much more saturated, warmer than Viridian Grim.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Intermediate Green is noticeably lighter, much more saturated, warmer than Viridian Grim.
The same difference applies the other way round: Viridian Grim is noticeably darker, much more muted, cooler.
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 Viridian Grim on the colour wheel See Intermediate Green on the colour wheel
All matches: Viridian Grim equivalents · Intermediate Green equivalents