We can't say each trophy is the most difficult to attain because each team have their own vision about the trophy they want. If you ask a player like Mbappe, he will tell you that the most difficult trophy to attain is the UEFA champions League, the same question goes to Lionel Messi, he will say that the most difficult one is the World Cup trophy because each trophy isn't easy to attain.

And I don't think any trophy can be characterized as being the most difficult to attain. All trophies are really hard to attain.

Thank you