His name needs no introduction. He is arguably the best coach of his generation but some might argue on the side of Jose Mourinho. No doubt both are definitely the best of the best. My choice of going with the former is simple, one thing he has better than Mourinho is better diplomatic management and good relationship with players which is indeed a key attribute every football manager should have.
Others argue that he is a failure because He never won the Champions league with Bayern, but I wouldn’t term him that considering the quality of opposition that stopped him from winning it. Reaching the semi finals isn’t entirely a failure, is it?
Some also argue that he is a coach that likes preying on already established teams therefore I would want him to prove himself at Manchester city next season by winning the league with them and taking them to their first Champions League Final or even winning it then and only then would He be the unarguably best Football Manager of all time.