I would agree that to win a championship as an individual champions league is the hardest, along with ufc/mma. Indeed You have to be better than all but a handful of people in the most played sport in the world, to get on the handful of teams that have a chance to win it. The level of talent on Barca, Bayern, Ajax, etc is just incredible. However, on the team level I don’t think so. There are, like I said, only a handful of teams with a shot, and those are the ones with the deepest pockets, and they have no salary cap to stop them from loading up on the best of the best. Just look at the list of winners, it’s pretty limited. I still think that World Cup is the hardest team sport to win. Worldwide, only occurs every four years, etc.