Surely, 2020 Bayern by Flick has to be somewhere in this conversation.
Flick left Bayern with one of the greatest winning records in modern football history.
During his tenure, Bayern lost just seven games and won seven trophies (Bundesliga twice, DFB-Pokal, Champions League, DFL-Supercup, UEFA Supercup, Club World Cup).
Bayern went undefeated in the 2019–20 Champions League, the first team in European/Champions League history to lift the trophy with a 100-per-cent win record, and won 23 matches in a row across all competitions between 16 February 2020 and 18 September 2020, a record in German professional football.
Flick also coached Bayern to a treble, the second treble in Bayern's history. Flick held one of the highest win rates in football history, winning 83% of his games and helped Bayern average 3.0 goals per game across all competitions.