The Knights had prevailed in dramatic fashion on Friday when Cole Shudra pounced with just seven seconds remaining against his former club to seal a 4-3 win.
But, last night at Ice Sheffield, Bonner put the hosts ahead with 23.04 on the board with some help from Matt Bissonnette and Jason Hewitt, the same combination coming together on the powerplay just over 10 minutes later when the former Hull Pirates forward doubled his tally for the night.
Leeds gave themselves a lifeline when Archie Hazeldine struck at 57.39, but the visitors’ hopes proving short-lived when Bonner sealed his hat-trick 40 seconds later.
There was still time for the Knights to apply more late pressure when Ben Solder made it 3-2 with 36 seconds remaining, but the Steeldogs prevailed.
On Saturday, the Knights picked up a first win in four tries in the league at Raiders.
After falling behind to a ninth-minute strike from JJ Pitchley, the Knights took control, going in at the first intermission 3-1 ahead through goals from Shudra, Kieran Brown and Lewis Baldwin.
Second-period strikes - both on the power play - followed from Matty Davies and Shudra before Adam Barnes got on the board with just under seven minutes remaining.