The 2023 grand finalists fell to their biggest loss of the year, conceding a run of nine unanswered goals after hitting the front in the second quarter to lose by 54 points on Thursday night.
It was the perfect response from the premiership-favourite Giants after last weekend's loss to Carlton, with their running game slicing up the Lions when they took over the contest.
Canberra local Tom Green put on another clinic on his home turf, racking up 36 touches, seven clearances and a goal to help his side continue surging towards the top of the table.
It was a second consecutive lethargic performance from Brisbane, having failed to handle rainy conditions in a 26-point loss against Geelong last weekend.
Lions forward Kai Lohmann snapped truly at the 19-minute mark of the second term to put his side ahead 42-39, with Brisbane appearing to have weathered an early storm and got back on track.
But the Giants had other ideas, generating momentum out of their defensive 50 and making the Lions look slow on their way to nine straight goals and a match-winning lead.
Irishman Callum Brown was in fine touch with three sweetly hit set-shot goals, with fellow forward Jake Riccardi also cashing in with a trio of majors.
Livewire debutant Darcy Jones lit up the Canberra crowd with a first game to remember, slotting a brilliant running goal in the first term on the back of his electric pace, before finding another late in the piece.
The Giants missed captain Toby Greene (suspended), key back Sam Taylor (concussion) and star midfielder Stephen Coniglio (knee), but still cruised to their sixth win of the season.
Brisbane got two first-quarter goals from Charlie Cameron to stick with the fast-starting Giants, and even hit the front early in the second when fellow forward Cam Rayner found a pair of his own.
The Lions missed ruckman Oscar McInerney (concussion), but did hold their own in the middle, but simply couldn't contain the GWS run when it got firing.
The Lions return home for a Queensland derby against the Gold Coast next weekend, quickly losing touch with the pack as they look to push towards another finals run.
Callum Ah Chee was subbed out at halftime with a hamstring injury.
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