彼は間違いを犯していた。

he; him; his; boyfriend

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

mistake; error; blunder; accident; mishap; trouble; improper conduct (e.g. between man and woman); indiscretion

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to commit (e.g. crime); to perpetrate; to make (e.g. mistake); to break (e.g. rule); to violate; to transgress; to contravene; to rape; to violate; to ravish; to deflower