I always found the CL to be very easy (at least until now, level 13). I had 5 finals, 3 wins and the other 2 I didn't care too much, lot's of 3rd places and semifinals at least.
Same for the league, I only rank below the 2nd position because I only want to rack up packs or money.
The cup has been my real struggle, but now I've won 2 in a row.

The treble seems much harder, I could have won one but lost the cup final to penalty kicks. Seeing as it's a lot harder now, I'm still regretting it.