The antonyms for the phrase "shining up to" could include words and concepts like ignoring, neglecting, avoiding, diminishing, tarnishing, or downgrading. When someone is "shining up to" another person, they are usually trying to impress them or gain some form of favor. The opposite of this behavior would be to disregard someone's opinions, avoid their company, or fail to give them appropriate attention. If a person or object is tarnished or downgraded, they can no longer be considered to have a shiny or impressive quality. In some cases, an antonym for "shining up to" might involve actively working against or opposing someone or something.