In one of his essays, Plutarch accuses Herodotus, another famed historian, of malice. Whether the specific charges are true is open to dispute, but the general outline he lays down is very insightful.
First, use of severe words when gentle ones will serve, derogative generalities, rather than specifics regarding the facts. For example, when he might have called Nicias “too much addicted to pious practices,” he called him “a fanatical bigot”.
Second, omission of what is good, creditable and relevant, and its reverse, inclusion of what is discreditable and irrelevant. To begrudge praise and to take delight in censure and misfortune are both objectionable.
Third, preference for the less creditable version, when two or more accounts of the same incident are current, or when the cause and intention of the deed are in doubt. For example, those who say that Cato committed suicide because he feared the horrible death which Caesar planned for him.
Fourth, when they detract from the greatness and virtue of people by denying that their deeds were done in a noble spirit, by hard work, by valour or by intelligence.
Fifth, when they attack people indirectly, shooting their slanderous shafts from under cover, as it were, and then turn round and withdraw from the fight by saying that they do not believe the charges which they certainly want other people to believe. By their denial they show themselves guilty of a mean spirit as well as a malicious one.
Sixth, when they qualify their fault-finding with some expressions of praise. Just as men who flatter with some degree of skill and finesse sometimes mingle expressions of gentle criticism, as a sort of seasoning to their flattery, so malice offers some preliminary praise to make its accusations seem convincing. For example, in his verdict on Socrates, Aristoxenus called him an uneducated, ignorant sensualist, and adding “but there was no real harm in him.”