Malevolent and maleficent are both adjectives describing wicked people or forces, but they differ slightly. Malevolence involves having ill will or wishing harm on others without necessarily acting on these feelings, while maleficence involves action intending to cause harm.
The words have opposites that similarly differ from each other. Benevolent, the opposite of malevolent, means bearing good will. Beneficent, the opposite of maleficent, means doing good or tending to do good. So malevolent and benevolent both primarily involve attitude instead of action, while maleficent and beneficent involve action.
Though the words share the root mal (i.e., bad), their immediate sources are different. Malevolent derives from the slightly older noun malevolence (meaning tending to wish ill on others), which comes from similar-sounding precursors in French and Latin. Maleficent comes from the now mostly obsolete noun malefice (meaning sorcery or an evil deed), which comes from the Latin maleficus.
The American bass-baritone makes a memorable villain, darkly malevolent in voice and manner, with impeccable German diction and projection. [Chicago Tribune]
Imagine a malevolent version of Ricky Gervais playing King George VI, instead of Colin Firth. [Independent]
He’s also, it should be noted, a super-intelligent vegetable from outer space, a sort of sentient, malevolent carrot with no mercy or emotion. [AV Club]
For the media reporting on Iraq it has been a matter of headlining the efforts of maleficent terrorists and burying the news of progress and successes, or not reporting them at all. [American Thinker]
[B]ut to reach it we have to slay the false self, the old man, which is informed by an actively maleficent agency, “flesh” which is hostile to “spirit.” [Christian Mysticism]
The young wife whom Douglas married, and the two children she bore him, also came in for part of her alleged maleficent enchantments. [Witch Stories]