Not sure if it's a dialectal/regional difference, but I think this expression be "out of pure malice". I think it's just a set phrase, because you can also have "he did something of his own volition" but that's not equivalent.
What a weird expression...
Out of pure malice
I made two errors with this which were not corrected!
Is ondskab neuter - rent ondskab?Help, I'm confused.