I thought we missed out a bit on some things in the finale, and in the entire series. Here are a couple of things I wanted to see more of:
Sokka in combat. We dont see Sokka fight that much even though he is a great warrior. You see him advance throughout the series from a fairly good warrior, then after meeting Suki and training in the North Pole, he becomes a skilled warrior. We see Sokka fighting a bit in Season 2, but not as much as I would have liked. In Season 3 Sokka finds a master and becomes a master swordsman. We got to see him fight in the invasion, but barely, and he does take out two firebenders who are all powered up with Sozin's Comet in the finale, but I would have liked to see more.
Retaking Ba Sing Se. Bumi Iroh, Pakku, those are some of the best characters in the series. Bumi is the most powerful earthbender, Iroh is one of the most powerful firebenders, and Pakku is the most powerful waterbender. All of these masters, and we only got to see a couple minutes of them retaking Ba Sing Se. Although Iroh summoning the huge fireball that broke clean through the walls of the city was awesome, and Jong Jong floating around creating pillars of fire was great as well, I wanted to see more of that.
List some things that you wanted to see more of in the series!