Alexander Zverev won his first title of the year by beating Felix Auger-Aliassime in straight sets at the bett1HULKS Indoors in Cologne.
The German, runner-up at last month's US Open, beat Canadian youngster Auger-Aliassime 6-3 6-3.
"I had a very tough final in New York and the next final I played here I wanted to come out and obviously play my best tennis, finish the match," Zverev, the top seed, said on court afterwards.
"Felix, you're an unbelievable player. I know it doesn't mean much right now, but I'm sure you are not only going to win one title, you're going to win multiple, multiple titles in your career, bigger titles than this.
"We know each other incredibly well. You're going to be lifting a winner's trophy very soon."
At the St Petersburg Open top seed Andrey Rublev took the honours.
The Russian world No 10, looking to stay on track for a place at the ATP Finals in London for the first time, beat Croatia's Borna Coric 7-6 (7-5) 6-4.
Victory also gave Rublev a big push in his quest to qualify for next month's season-ending ATP Finals for the first time and the Russian will move up to eighth in the world rankings.
Two spots remain to be filled as Rublev leads Argentina's Diego Schwartzman, who currently occupies the final qualification position.
The ATP Finals begins on November 15 and is set to be played behind closed doors.
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Serbia's Laslo Djere won the Sardegna Open with a 7-6 (3) 7-5 victory over Marco Cecchinato of Italy.
"I'm very happy for this," he said. "I stayed very focused on my game during the match from the first to the last point. There are so many positive things from the past few weeks."
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