1. Sean McDermott (2017-2022)
While Sean McDermott may be a polarizing figure among Buffalo Bills fans he is easily the best head coach since 2001 and probably the best in franchise history right now behind only Marv Levy. The Bills would hire McDermott prior to the 2017 season to be the next head coach after firing Rex Ryan during the season.
McDermott was a long-time defensive coordinator and was able to turn around the franchise almost immediately as they would make the playoffs in his first season with the team. Since that season, the Bills have won three AFC East Championships and four playoff games.
He also has the best winning percentage in franchise history at .639 and is only six wins behind Lou Saban in terms of all-time wins in Buffalo Bills history.
There have certainly been missteps in Sean McDermott's time as head coach and decisions that he probably wishes he could have back. However, his resume over the past six seasons should speak for itself and he should be considered one of the better coaches currently in the NFL.