Use the adjective one-time to mean "long ago" or "former." For example, a one-time movie star was famous in the past, but might not be recognized today.
A one-time chess champion might have won competitions years and years ago. A one-time international spy may have had exciting adventures in her youth, although today she could very well be an unassuming elderly lady. The one-time star of a basketball team isn't anymore, and a one-time dog owner might have switched to keeping cats instead.