For me personally this one.
>>Units will no longer be dismissed when you lack the Food to maintain them!
It means I can actually play the game.
I couldn't do anything for nearly two months outside of launch league strikes at beacons.
It means me a modest spender not a giant coiner can still play the game. It's balanced the end game between "players" and coiners meaning both can still participate. Very very good for the game (although I know a lot of people shortsightedly hated this updated without truely understanding its impact).
And my worst updates - closely connected to eachother.
>>Changes to Battleground mechanics!
>>Global Tournaments!
I hugely miss the old BG quests. Better reward (over twice the reward), and then there was the 15k/30k sapphire reward for top 30. Really provided players with an incentive to get big at BG's and reward their time and endevour. It also made it possible for non-coiners to outplay the coiners at something for an advantage that somewhat leveled the playing field.
When they nerfed both the profit from BGs (I think quite unwittingly and unintentionally) with the 10% payout update and drastically nerfed the BG quest reward Plarium massively shifted the balance of the game to coiners.
The 2 months prior to updates I had made approx 10m army power a month - after its 3m max +whatever quest rewards you earn. Simultaneously they released perminant massive discounts and 75% healer discount, effectively cutting sapphire costs by 75-80%. Horrible couple of months for the direction of the game (followed by introduction of coining items in the shop).