Hmm since Ive been going Ive these to pick from..
1984-1989
Lou MACARI
285 138 67 80 449 340 60%
1989-1991
Ossie ARDILES
106 40 33 33 163 140 53%
1991-1993
Glenn HODDLE
120 51 32 37 202 162 56%
1993-1994
John GORMAN
72 15 20 37 90 148 35%
1994-1998
Steve MCMAHON
204 75 49 80 245 277 49%
1998-2000
Jimmy QUINN
85 19 21 45 84 141 35%
2000
Colin TODD
18 4 6 8 16 29 39%
2000-2001
Andy KING
36 12 10 14 43 43 47%
2001
Roy EVANS
26 10 6 10 30 35 50%
2001-2005
Andy KING
193 71 48 74 265 263 49%
2005-2006
Iffy ONUORA
40 10 15 15 40 56 44%
May-Oct 2006
Dennis WISE
17 9 5 3 24 14 68%
Nov 2006 - present
Paul STURROCK
32 18 6 8 40 27 66%
So according to the success % the worst is Gorman or Quinn.
In all honesty I didnt go during the Premiership but Gorman never had a hope in hell so his percentage for that season shouldnt really count.
Quinn,Iffy and certainly in his second spell Kingy were in impossible situations so kingys percentage prooves he was ace.
So i'll plump for Todd because what he left was by and large a complete load of wank.