Early 17th century; earliest use found in Philemon Holland (1552–1637), translator. Either from classical Latin maleficus + -ial, or formed after beneficial with substitution of classical Latin male- badly for bene- well.
Definition of maleficial in US English:
maleficial
adjectiveˌmalɪˈfɪʃl
archaic
Malefic, maleficent.
Origin
Early 17th century; earliest use found in Philemon Holland (1552–1637), translator. Either from classical Latin maleficus + -ial, or formed after beneficial with substitution of classical Latin male- badly for bene- well.