For me , with (dis)honourable mentions to the Dick, and DJ there is a clear winner in my 30+ yrs watching the Jags.....step forward Sandy Clark.
Took a team with one league defeat (in the game before he was appointed away at McDiarmid) to winning 2 of the next 17. Included in that shambles was a 5-4 Hogmanay humping from Albion Rovers ffs....despite being 2 up after 3 mins and also leading 4-2 as I recall.
Archie showing up pretty well so far as stats below show (great site for the statto's amongst us!)
http://www.fitbastats.com/partickthistle/manager_games.php?id=16
http://www.fitbastats.com/partickthistle/manager_records.php