Tell me...what is more awesome than defeating The Bittercold, an entity made up of all the negativity and suffering of all the Pokemon worldwide, ALL BY YOURSELF?
The partner deserves a mention too. Though the best he can do is offer moral support in the final battle, the fact that he managed to make it all the way to the Bittercold's chamber despite it making it hard for him to breathe long before they ever got close, which includes during the battle with Kyurem, before it finally becomes too much for him is rather a nice testament to how much he wants to help his friend and save the world. Especially when compared to the previous time they were there, when they barely got halfway before passing out.
The partner's journey to the Worldcore in the postgame can be considered this and a Crowning Momentof Heartwarming. When the partner gets to the Hill of Universal Order, the partner wishes that the player can travel between the human world and the Pokémon World, which causes the Hill of Universal Order to nearly collapse until the player yells out that the player wants to return to the Pokémon World. Then, the player comes back in the same Pokémon body like it was picked at the very beginning of the game. So basically, the partner's wish fulfilled successfully when the partner believed so greatly. Now THAT is awesome.
During the part before you rescue your partner, you manage to KO Toxicroak. WITH YOUR BARE HANDS!
Hell, the fact the player character and Hydreigon coming up with this plan and outgambiting Munna on short-notice is made of this. Especially considering Hydreigon knew he was going to escape with the PC and partner in tow, when the former alone tired him out.
Each time Hydreigon pulls a Big Damn Heroes moment, but especially the first, when you can't even be sure he's even real, much less on your side.
And let's not forget the part when Hydreigon pulls the second Big Damn Heroes moment where Hydreigondoes a barrel roll to dodge the Salamence that is going after Hydreigon. Awesome indeed.
And the post-game legendary battles? The animations before the legendary fight and when they are defeated are awesome!
Honestly, all the graphics in the game are pretty beautiful. Especially the Rainbows of Hope near the end of the game.
The Crags of Lament not only have the second most awesome dungeon name in the game (after Jaws of the Abyss), but they are the first dungeon in the game without walls. Instead, you're walking on beautifully rendered CLIFFS.
Swanna deserves some mention for being one of the only Pokemon in Post Town to not lose their head when the team tells everyone that the world might be destroyed.