From Longman Dictionary of Contemporary Englishbe at the height of your success/fame/powers etcbe at the height of your success/fame/powers etcBESTto be more successful, famous etc than at any other time The Beatles were at the height of their fame. → height
Examples from the Corpus
be at the height of your success/fame/powers etc• By the 1860's, when he was at the height of his fame, tragedy struck as he took increasingly to drink.• However, in 1985 he was at the height of his fame as a novelist.• Outwardly, the Cowboys appear to be at the height of their powers. 