I think an underatted team was Ac Milan from 2003-2007, they had a lot of talented players. They had such a great defense and offense. They had superstars all over with guys like Pirlo, Gattuso, Nesta, Cafu, Dida, Kaka, Shev,Crespo. Spain struggled against Italy a few times (2008 and 2012) which shows that Italian football style would have been an issue for Barcelona if they faced them more often.
Bayern 2020. The most dominant team in football history by far