déplorer

To deplore or express deep regret about something, typically in formal or written registers — a journalist, official, or organization déplore des violences, des pertes, une décision, expressing strong disapproval or sorrow rather than casual sadness.

• Le maire a déploré la violence des affrontements. — The mayor deplored the violence of the clashes.
• Nous déplorons ce retard dans les secours. — We deplore this delay in the rescue effort.
• Les organisateurs déplorent l'annulation de l'événement. — The organizers regret the cancellation of the event.

This is formal/written register — in everyday speech about being sad, French speakers reach for être triste or regretter, not déplorer, which sounds stiff in casual conversation.