Hosts Argentina roared to a superb 47-26 victory over defending champions France as pool play concluded at the World Rugby Under-20 Championship.
The result at the Racecourse Stadium in Rosario saw the home side qualify for the semi-finals as Pool A winners as the last four line-up was decided.
Despite their defeat, France still made it through as the best runner-up across the three groups and will meet South Africa, with Argentina now locking horns with Australia.
Argentina knew that only a victory would keep their hopes of progressing alive and the job was essentially done by half-time as they raced into a 34-7 lead.
Four first-half tries earned a bonus point as Thomas Gallo, Gonzalo Garcia, Juan Martin Gonzalez and Pablo Dimcheff all crossed the whitewash.
Gallo's sublime 60 metre try was the highlight of a half which also saw red cards for both sides.
Flanker Sacha Zegueur was dismissed for the French for a high tackle before Argentine winger Rodrigo Isgro received his marching orders for a near-identical offence.
France, who had Quentin Delord's try to show for their first-half efforts, rallied with three more in the second half to earn an important bonus point.
Argentina crossed just once again through skipper Juan Pablo Castro but the damage had been done as Joaquin de la Vega Mendia ended with 17 points from the kicking tee.
Jordan Joseph, Donovan Taofifenua and Matthis Lebel were the French try scorers after the restart as Louis Carbonel contributed six points with the boot.
"It was a really good win," said Castro.
"The crowd were amazing.
"Now we're already thinking about the next game."
In the other Group A game, Wales beat winless Fiji 44-28 to finish third.
Like Argentina and France, they also finished with two wins from three but their lack of bonus points saw them end on a total of nine points, with the top two on 11.
The hosts won the group on points difference as they reached a third semi-final at the competition.
In Pool C, South Africa beat New Zealand 25-17 in a winner-takes-all clash at the Racecourse Stadium which decided who topped the pile.
Vaughen Issacs' eighth-minute try set the South Africans on their way and JJ van der Mescht crossed again for them after a fine burst from halfway.
South Africa were able to keep their opponents at bay despite the loss at one stage of three-men to the sin-bin, with a penalty try and Lalomilo Lalomilo's score proving in vain for the Kiwis.
They suffered a cruel late blow as a collapsed maul allowed Sanele Nohamba to kick a South African penalty which denied New Zealand a bonus point for losing by no more than eight.
This would have taken them through to the semi-finals instead of France but they instead ended on 10 behind South Africa's 14.
"It was massive game for us, and credit to the New Zealand side, they pushed us all the way," said South Africa captain Phendulani Buthelezi.
"I'll be honest, our discipline let us down today but I'm proud of the way the boys responded and stuck together.
"We're going to focus on our recovery now and make sure we hit the ground running in the semi-final."
Georgia beat Scotland 17-12 in the pool's other match which saw both sides hoping for a first win.
In Pool B, Australia already knew that they were through with a game to spare but they ended with a big 56-33 defeat to an England side smarting at already being eliminated.
England, finalists for the last six years, ran in eight tries at the Club De Rugby Ateneo Inmaculada in Santa Fe but finished third in the pool.
Ireland came second by beating Italy 38-14.
The semi-finals and classification matches will take place on Monday (June 17).