赞成 is the formal opposite of 反对 (fǎnduì, to oppose). They're often paired in discussions and votes: 赞成的请举手 (those in favor please raise your hand).
mistakes
Don't confuse 赞成 (approve/agree with a proposal) with 同意 (tóngyì, agree in general). 赞成 implies active endorsement, while 同意 is more neutral agreement.
