That depends on what you exactly mean. Maleficium means an evil deed, wickedness, crime, and malitia means badness. Malum, which is an adjective, can also mean evil as a substantive. Scelus is an evil deed or wickedness and is a much stronger word than a word like peccatum, which means a sin. Sceleritas is the act of committing an evil sin, or wickedness. Some latin words can mean both evil or an evil deed.
The best might be malum, due to the Vulgate (and it is the closest in use to our word evil) and maleficium because in Medieval times maleficus and malefica meant a male witch and a female witch, but in a way in it meant harm, sorcery, or fraud, so, yay, malum might be best.
"Ego sum malus."
"Dead king" in English translates to "mortuus rex rgis" in Latin.
Curse. "Malediction" comes from Latin for "bad" (or "evil") and "say."
Rex Iudaeorum
You say 'Tuus rex est.'
rex regum
Filia regis is daughter of a king
There is no Latin word for princess. The nearest is regis filia which is the daughter of the king.
Rex mei mundi.
Boondock Saints reference....
Rex bestiarum (I think)
While I can't say for certain what was behind the choice ... the meaning is pretty obvious to anyone who knows Latin. "Bene-" is the Latin root for "good" and "Mal-" is the Latin root for "evil", so "maleficent" is like "beneficent" except ... y'know ... evil instead of good.