Germany is probably going to be the biggest rival of Brazil in this world cup in my mind. Miroslav Klose scored the 2 - 0 for Germany in that 7 - 1 match against Brazil, surpassing Ronaldo's world cup goals record, and they ended up winning that world cup... it was devastating for Brazil.
Although some other teams might be even worse for Brazil:
Interestingly, Brazil has never won in the world cup against these three teams: Switzerland, Portugal, and Hungary.
And The Netherlands has won 3 times against Brazil in the world cup, with only one loss and one draw. The Netherlands seems to be the most difficult team for Brazil.
Miroslav Klose retired almost a decade ago, and there is no point in talking about him. And IMO, Germany is not one of the top-4 teams at this moment. For me, they are much weaker when compared to Brazil, Argentina, France and England. And I find it funny that Brazil has never won against teams such as Hungary. That maybe because they have played fewer matches between each other? And Hungary was extremely strong when they had players such as Ferenc Puskás. When was the last time these two teams met?