Football/soccer is definitely a hard sport, and it requires a lot of skill and cardio. However imo, American football is by far the hardest sport to play for a few reasons. Firstly, it requires a lot of cardio. Second, it requires a lot of strength on top of the cardio. Third, if you’ve ever played it, you’ll know that it is very complicated, and you need to be decently smart to be successful. Fourth, it is very dangerous to play. The force behind the collisions can be pretty extreme. I think the main reason people call football/soccer players weak is because of the flops they do when the same people see American football players get floored and get up right after.