Write from facts rather than momentum
Pause long enough to remove accusations, assumptions, and details that belong to someone else. For a message about how to apologize for missing a community shift, use this factual base: state the date, place, property, noise, pet, or shared-space impact without arguing about the neighbor's character.
Offer a proportionate next step
Match the size of the request to the relationship and to what the recipient can reasonably decide now. Offer cleanup, replacement, access, a schedule, or another practical remedy you can complete. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Protect privacy on both sides
Do not threaten, shame the neighbor publicly, or involve the whole building in a private issue. Use property management, local authorities, or emergency services for genuine danger rather than confronting someone unsafely. Use the most private legitimate channel available and do not share the exchange to recruit support or pressure.