Needing a win to maintain their slim hopes of a wild card spot, GWS kicked nine straight goals as they charged to a 16.15 (111) to 7.15 (57) victory at Engie Stadium on Sunday.
They turned a 16-point first-quarter deficit into 35 and 47-point leads at half and three-quarter time.
West Coast slumped to a 10th straight loss despite winning the clearances and racking up the same number of inside 50s.
Their lack of accuracy across the two middle quarters proved costly with GWS kicking 8.5 to 0.9.
With questions over the futures of Toby Greene, Jesse Hogan and Jake Stringer, GWS showed they had other goal-kicking options up forward, though Green contributed two majors.
Callum Brown booted four goals, Aaron Cadman three and Harvey Thomas and Riley Hamilton two each.
Both teams kicked five goals in a frantic first quarter in which West coast had seven more inside 50s.
The Eagles dashed to a 16-point lead on the back of four straight goals, with Tom Cole involved in all of them, as the visitors scored primarily from back half chains.
GWS retaliated by kicking four of the last five goals of the term to lead by one point at quarter time, with four majors coming from clearances.
The Giants carried the momentum Into the second quarter, kicking. 6.2 to 0.5, with their running game and drive from the back half cutting the Eagles apart.
Eagles spearhead Jake Waterman had another mixed outing, kicking 2.3 and Liam Baker also kicked two goals.
GWS half backs Lachie Ash and Lachie Whitfield tallied 36 and 33 touches respectively.
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