Leiderweise
Leiderweise is a German adverb meaning “unfortunately” or “in an unfortunate way.” It is formed from the word leider, meaning “unfortunately,” combined with the suffix -weise, which means “in a manner.” The result is a somewhat formal or literary expression used to emphasize that a consequence occurred in an unwanted or regrettable way.
The term is more common in written German and in formal prose than in everyday speech, where
Leiderweise musste der Termin verschoben werden. — Unfortunately the appointment had to be postponed.
Die Lieferung kam später als angekündigt; leiderweise war der Empfänger nicht erreichbar. — The delivery arrived later
Leiderweise konnte ich aus gesundheitlichen Gründen nicht teilnehmen. — Unfortunately I could not participate for health reasons.
Bedauerlicherweise and unglücklicherweise are common synonyms that express regret and may be preferred in equally formal