"Doeth a number on" is an idiom used to describe a situation where someone has caused significant damage or harm to someone or something. Some antonyms for this phrase could be "heals," "repairs," "ameliorates," "restores," or "reinstates." These words all connote actions that lead to improvement or positivity. For example, a person who "reinstates" a sense of trust in a broken relationship is working to repair the damage that was previously done. Similarly, a doctor who "heals" a patient is taking steps to bring them back to good health after a period of illness or injury. These antonyms serve to offer a more positive outlook on situations where "doing a number" might have occurred.