ΔE 24.8, loose: different enough that you should pick on purpose. Murderous Magenta is a little darker, more muted, cooler than Blood Thorn.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Murderous Magenta is a little darker, more muted, cooler than Blood Thorn.
The same difference applies the other way round: Blood Thorn is a little lighter, more saturated, warmer.
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 Blood Thorn on the colour wheel See Murderous Magenta on the colour wheel
All matches: Blood Thorn equivalents · Murderous Magenta equivalents