General synonyms:
* Spite
* Viciousness
* Malevolence
* Ill will
* Hatred
* Animosity
* Rancor
* Grudge
* Meanness
* Wickedness
Synonyms emphasizing intention:
* Deliberate harm
* Intentional cruelty
* Malice aforethought
Synonyms emphasizing action:
* Vengeance
* Retribution
* Revenge
Synonyms emphasizing feeling:
* Bitterness
* Resentment
* Envy
The best synonym for malice will depend on the context of your sentence.