Green’s Dictionary of Slang

(UK black/W.I.) ruthless, malicious; envious, wishing someone ill; also adv.

1926		E. Walrond Tropic Death (1972) 120: ‘Yo nasty t’ing yo’!’ ‘Yo’ murrah!’ ‘Bad-minded wretch!’.
1993		E. Sobo One Blood 99: ‘Bad mind’ people actively try to ‘spoil’ those they grudge.
1995		Francis-Jackson Official Dancehall Dict. 2: Bad-mind envious; wishing someone ill: u. bad-minded person.
2020		G. Krauze What They Was 53: You just have to be more savage, more badmind [...] and then bang — you’ve got your own reputation.
2020		G. Krauze What They Was 210: Moving so badmind that the wickedness you do come like you got no heart [...] to feel anything.