Callan Ward won a controversial free kick and then booted the winning goal as GWS overcame a historically slow start to wind in a 29-point margin and remain in the AFL's top eight with a win over Essendon in the wet on Friday.
The Giants and Bombers managed just four points between them in the first quarter at Metricon Stadium - the lowest-scoring opening term since 1965.
But the Bombers broke the contest open with five straight second quarter goals, stretching that lead again early in the third term before their offence slowly disappeared in a 8.11 (59) to 8.7 (55) victory.
The Giants kicked just two first-half goals but Essendon did the same in the second, the win keeping the Giants in seventh and the Bombers just outside the eight.
Two final-quarter Jeremy Cameron goals and Heath Shaw's first two-goal bag in eight years dragged them back, before recalled veteran Ward won a free kick and drilled the long-range goal for a 10-point buffer.
It meant the impressive Adam Saad's huge bomb in the final seconds was in vain.
Ward collided theatrically with Shaun McKernan and was awarded the free kick, admitting in a post-game interview with teammate Shaw that he "thought I played it pretty well ... I didn't 'play' for it, but I knew the contact was coming."
It came hours after Sydney's Tom Papely was fined by the AFL for staging, Bombers coach John Worsfold resisting the urge to question the decision post-game after his opposite Leon Cameron went in to bat for the 222-game veteran.
"His second half was really spot on and for him to kick that goal at such a crucial time and give us a little buffer clearly made the difference," he said of Ward.
"There's going to be ... 30-40 free kicks throughout the game and there will be one side disappointed and another happy.
"But I thought our endeavour for the last 30, 40 minutes of that game willed us over the line.
"When you're playing with that momentum normally that run of the ball (with decisions) can go your way."
Giants veteran Shaw provided the talking point of a dour first quarter when his bump on Jacob Townsend ended the Bomber's evening in sickening fashion.
Phil Davis was thrown forward to stop the Bombers' run and it worked as he helped set up a Jeremy Finlayson goal.
Davis was soon hopping off with a knee injury, but was able to return as they went about their recovery.
"Over the course of the full game we couldn't maintain that pressure on them on the scoreboard," Worsfold said.
"We couldn't hold them ... there wasn't a sense of that (regret at not taking a risk to win it), but it's something we need to be aware of because we scored well in that second quarter but not after that."
The Bombers next play on Wednesday against Gold Coast while the Giants travel to Perth to play Sydney next Thursday.