#4. Barcelona (2002-03)
During the 2002-03 season, Barcelona had a mediocre La Liga season, finishing 22 points behind their rivals, Real Madrid. However, they were unstoppable in the Champions League. This edition of the tournament had two group stages, and Barcelona managed to finish the first group stage without dropping any points.
Barcelona was drawn into a relatively easy group, featuring Club Brugge, Galatasaray, and Lokomotiv Moscow. Despite their easy draw, their domestic form raised concerns among Barcelona fans at the start of the Champions League campaign. They started with a 3-2 win against Brugge and followed it up with a comfortable 2-0 victory over Galatasaray.
The strongest team in the group was Lokomotiv, but Barcelona won both matches against them (1-3 and 1-0). After winning a close match against Brugge at Camp Nou, Barcelona had to face them away from home. It was another close match, but Barcelona clinched all three points with a 1-0 win. In their final match against Galatasaray, Barcelona easily won 3-1, achieving a perfect record in the group stage.