I think fans of great teams all feel like their team had missed a few spectacular oppurtunities to win another ucl. Be descriptive on which season and why you think they should have won it. For me its gotta be liverpool 2022, even though we were lucky to get to the final because we played easy teams, I still feel like we failed badly against a wounded Madrid team. I felt like Firminho should have started in the center, but they used Mane instead. That imo was the reason we lost that game. Madrid deserved the win because they went through harder opponents, but within that match itself we had no excuses to lose.
Man United here.
2003/04 season - Paul Scholes had a perfectly good goal disallowed in the second leg against Porto. If that had stood and we had won that, arguably Monaco were the only other team to fear. As it happens, Porto won, and basically thrust Mourinho on the world.
2012/13 season - Nani should never have been sent off when we were leading at home to Real Madrid. Completely changed the match in an instant. We had a real shot at that UCL that season.