Souths' pack were winning the forward battle to leave Canterbury struggling for territory while Reynolds was relentless in pressuring Canterbury's back three of Sam Perrett, Corey Thompson and Josh Morris, with kicks along the ground and in the air, yet the six-point margin remained at the break.
A Canterbury mistake off the kick-off gave Souths the perfect start to the second-half but the Bulldogs remained in the fight and sniffed an opening when centre Dylan Walker lost possession.
Canterbury worked it into position before Josh Reynolds threaded a grubber through for Williams to collect and score, with halfback Trent Hodkinson's conversion levelling things up.
The momentum looked to be shifting but the Rabbitohs powered back in front when Burgess busted through four defenders to score under the bar, with Reynolds' goal restoring their six point lead.
A shoulder charge from Graham saw Adam Reynolds awarded a shot at goal which skewed wide but he nailed his next shot moments later, after Aidan Tolman was penalised for holding on.
Canterbury's hopes were extinguished when Auva'a touched down off an Inglis kick, before Reynolds and Inglis capped the scoring to spark jubilant scenes of celebrations.
SOUTH SYDNEY 30 (K Auva'a G Burgess G Inglis A Johnston A Reynolds tries A Reynolds 5 goals) bt CANTERBURY 6 (T Williams try T Hodkinson goal).