According to Pearson Education Inc., USA the CA(India) final exams are one of the toughest exams in the world. There are 10 of them in this list. CPA(USA) is also included in this list.
Pearson is a large education company listed on NYSE and employs about 40,000 people.
Here is the link:
https://www.talentlens.com/en/posts/worlds-toughest-tests.php