彼はありを退治しようと思った。

he; him; his; boyfriend

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

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about

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.

extermination (e.g. of pests, demons, bandits); elimination; eradication; suppression; making someone renounce worldly desires in order to concentrate on Buddha's teachings; curing illness

if; when; and; with; particle used for quoting (with speech, thoughts, etc.); quoting particle; promoted pawn; indicates question (sentence end)

to think; to consider; to believe; to think (of doing); to plan (to do); to judge; to assess; to regard; to imagine; to suppose; to dream; to expect; to look forward to; to feel; to desire; to want; to recall; to remember