He used to bully his friends.
Kare wa yoku yūjin o ijimeta mono da.
he; him; his; boyfriend
topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis
nicely; properly; well; skillfully; skilfully; frequently; often
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 tease; to torment; to persecute; to chastise
be; is; indicates past or completed action; indicates light imperative