It is a close call between Lawrie McMenemy and Ted Bates. I saw the team under both managers. Ted took us up twice and into Europe, while Lawrie took us back up, won the FA Cup, got us to the final of the League Cup and under him we finished second in the top division with that memorable win at Notts County (where i was with my brother).
On balance, i would probably go with LM as his achievements seem a little greater than Ted's - but i could be persuaded the other way.