The 3-7 season was also during the shortened COVID year and was an SEC-only schedule, so at least he won 3 conference games that year. IMO the worst season in school history was 2017 under Butch; winless in conference play for the only time in school history.
I'd have Dooley ahead of Pruitt on this list. It's a low bar, but Pruitt at least got the team off the mat after starting 0-2 in 2019 and won 7 regular season games and then a bowl game, admittedly against not great competition (but we weren't good either). By comparison the high point of Dooley's tenure was probably beating NC State in the 2012 season opener, or beating Vandy in OT in 2011. That makes me sick to my stomach to even type that.
They each brought their bad mark to the table. The worst overall coach of the three was Dooley. The single-worst season was under Butch (2017). The single-most embarrassing loss was under Pruitt (Georgia St).