The antonyms for the phrase "be the service of" are "act against," "oppose," and "harm." These words suggest a lack of willingness to help or assist someone or something. They imply a sense of hostility or negativity towards the subject of the sentence. If one is "acting against" or "opposing" someone or something, they are actively working to hinder or obstruct the progress of that entity. Similarly, if one is "harming" something or someone, they are causing damage, detriment, or injury to that subject. In contrast, to "be the service of" someone or something implies a sense of aid or help, suggesting that one is working to benefit or support that entity.