Season 7, otherwise known as The Season of Leaks. Not to mention the movie that was leaked online in HD.
 
This season finale is, in my opinion, the best. It has, by far, the least number of things that can make people upset. Putting aside Season 1’s finale, every single finale before Season 7 has made a number of viewers…angry.
 
Season 2: Twilight has a brother out of nowhere.  
Season 3: Twilight’s wings  
Season 4: Twilight’s castle  
Season 5: Starlight’s redemption  
Season 6: Changelings turned into jellybeans
 
And of course Star Swirl was angry at Twilght for meddling with his efforts, and he was right to get angry, but at least he apologised in the end and recognised Twilight’s achivements.
 
Edit: The lighting on Twilight’s face is a bit off. The edited version is on my dA page.