In a manner involving or resembling flogging; with severe beating or punishment.
From 'flogging' (the present participle of 'flog') plus the adverb-forming suffix '-ly' (in the manner of).
Adding '-ly' to a gerund like 'flogging' to make an adverb is grammatically possible but creates an archaic, brutal-sounding word that you'd never use in modern English—it's almost onomatopoetic in its violence!
Complete word intelligence in one call. Free tier — 50 lookups/day.