Coach Leon Cameron has hailed GWS' character in bouncing back from a rough start to the AFL season to grind out a 30-point win over Collingwood.
Stand-in captain Toby Greene booted five goals to inspire the injury-hit Giants to a superb 14.6 (90) to 9.6 (60) victory and get their campaign off the mark.
The Giants were 0-3 heading into Saturday night's game, and reeling from injuries - before Greene, who Cameron lauded as a "special player" and his inexperienced teammates condemned Collingwood to their second-straight loss.
"Really proud win because we could've probably rolled in here and had a really good, solid performance with an extremely young team," Cameron said.
"We haven't had a team like that since 2015 - so extremely young.
"Sometimes it's a danger - you get to halftime or half-way through the third and you've had a good crack but then you fizzle out and you don't get the job done.
"Just extremely proud for them to find a gear, especially when we were under the pump halfway through the last - and then we kick away.
"I thought the intensity of the night from all 22 was first-class.
"... It was an unbelievable effort, clearly, offensively, to do what (Greene) did, but to to marshal the troops when we were under the pump, I thought was fantastic."
It was a dirty night for Collingwood who slipped to 1-3 and had vice-captain Taylor Adams limp off with an MCL injury in the third quarter, while Brayden Sier (gastro) was substituted out for Levi Greenwood earlier that term.
In his first game for the season, veteran ruckman Shane Mumford limited the influence of Magpies star Brodie Grundy, while Callan Ward pushed through a first-quarter hand injury to rack up 37 touches and seven clearances.
The Giants burst out of the blocks when Bobby Hill soccered through the opener - but Collingwood responded through debutant Beau McCreery's toe poke.
In a cagey first quarter there was no more scoring action until Finlayson nailed a long-range set shot after the siren.
Greene snared three goals in the second quarter, then two after halftime to help stretch GWS' lead beyond four goals in the teeming rain - before a previously listless Collingwood struck back.
Jordan De Goey and Josh Daicos provided a spark, with Will Hoskin-Elliott adding another goal before Harry Himmelberg's strike gave the Giants breathing space at the final change.
From there, the Giants held firm, then kicked away late - leaving Collingwood coach Nathan Buckley to rue the Magpies being "belted up at contested ball."
"We just didn't win enough contests - just did not win enough contests," he said.
"It looked like in the third quarter there that we had our game going and it looked for all intents and purposes that we were going to be able to grind the result out.
"But when we encountered some resistance there, through the middle part of the last quarter, then we ran out of puff."
Australian Associated Press