Austria's Dominic Thiem, playing his first final in nearly three years, was swept aside 6-3, 6-1 by Argentine Sebastian Baez in Kitzbuehel on Saturday.
Former world No 3 Thiem had sunk to the depths of the rankings, to 352nd in 2022, two years after his US Open triumph.
The 29-year-old has been fighting his way back after a wrist injury, and was ranked 116th when he arrived in Kitzbuehel after losing nine of his 10 matches played in 2023.
He showed fatigue after a marathon three-and-a-half-hour semifinal against Serb Laslo Djere, where the 2019 champion saved five match points.
His Argentinian rival, ranked 72, dominated the rain-delayed tie for his third career title after Cordoba this season and Estoril last year, all on clay.
The 22-year-old raced to a 4-1 lead in the opening set, and reeled off four straight games in the second, converting four of six break points, to win through in 80 minutes.
With his title run, the Argentine has risen 25 spots to 47 in the ATP rankings.
Thiem is set to return to the Top 100 on Monday to 89th.