The 30-year-old midfielder set up the win with three goals and 18 disposals in the first half.
He finished with 33 possessions, 11 inside 50s and 11 score involvements as the Dogs ran out 21.8 (134) to 7.11 (53) winners at Marvel Stadium.
"It's rare that I stand in front of the group and blow smoke, because I don't want him to feel uncomfortable," Beveridge said.
"But after today, it was necessary to definitely acknowledge how well he played.
"He was quite incredible, really."
With midfielders Tom Liberatore (29 possessions) and Matthew Kennedy (27) following Bontempelli's lead, the Bulldogs monstered GWS in the clearance battle, 45 to 26.
As the Dogs' midfield controlled the flow of play, forward duo Aaron Naughton (six goals) and Sam Darcy (four goals) took full advantage.
The Bulldogs extended the margin at every change, from 16 points at quarter time to 38 at half-time and 58 at three-quarter time, finishing as 81-point victors.
GWS coach Adam Kingsley lamented his side's lack of fight, having now lost 10 of their last 11 matches against the Bulldogs, admitting Saturday's defeat was almost a "carbon copy" of their 88-point loss at the same ground last season.
Skipper Toby Greene worked hard for the Giants, winning 26 disposals, playing mostly through the midfield, but lacked support.
"He started really well. Without the same level of finish as Bontempelli had in the first half, the numbers were similar," Kingsley said.
"I thought he was one who did show some fight, and tried to do something about it.
"But we've got to get more on the bus."
There were few other positives for the Giants, though Finn Callaghan showed no signs of rust after missing training with soreness during the week, kicking two goals and winning 27 disposals.
After just two wins from 11 matches against top-eight teams in 2025, the Bulldogs have started 2026 with the scalps of two of last year's finalists, after beating Brisbane in Opening Round.
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