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According to a report in 012 Duodecim, while Cloud was a warrior of Chaos he once saved Tifa from Sephiroth. Despite her not recognizing him, Cloud is spurred by the meeting into realizing he's on the wrong side. So he picks a fight with Chaos. Lying defeated and fading away, Cloud uses the last of his strength to tell Cosmos to protect Tifa. Cosmos is so touched by this that she promises to bring him back on her side next cycle.
The ending. They all get to go home at last. It's simple but astonishingly effective.
Especially when the Warrior of Light walks off. It was one big Shout-Out to the opening sequence of Final Fantasy I, where it all began. This reminds us what the game is: an anniversary game, and what better way than to basically do an HD reenactment of where it all started?
Bonus! When the warriors are saying their final farewells to each other, they do so in descending order. Tidus (hero of the 10th game of the series) says goodbye first, followed by Zidane (9th), then Squall (8th), and so on... until it's the Warrior of Light's (1st) turn. It's like a countdown to the very beginning of the series.
Their respective farewells say something poignant about what they'd learned, some short and succinct, but all of them where heartwarming (even Cloud's).
Tidus: (notices his crystal glowing and sadly notes) Gotta go huh? (turns to the others and smiles) Don't worry, the crystal knows the rest of the way. Besides, I'm always right here.
Kuja's Shade Impulse ending. Lamenting that the world has disowned him, he asks Zidane to erase his pointless existence, but instead he tries to help him up, with his trademark line "Do I need a reason to help someone?" while adding "Or is my help not good enough for you?" Even though Kuja refuses, it's not out of arrogance. He essentially tells Zidane to forget about him and go on with his own life as he vanishes into blue flames (the sign of redemption, as most of the villains vanished into purple flames). And yet, Zidane still promises they'll go back together eventually. Even the awkward Lip Lock does little to diminish the heartwarming.
In 012, it's revealed that Kuja was the one who first broke Kefka's spell on Terra in a brief moment of empathy, because her servitude to Kefka reminded Kuja of his own Dark and Troubled Past.
Minor one: after defeating Chaos, all the heroes begin to fade away into pyreflies. Before vanishing, you can see what appears to be Terra comforting the Onion Knight.
In a side scene in Duodecim, Laguna counters Squall's assertion that there's no point in getting to know the other warriors since they'll all be going back to their own worlds anyhow:
"Listen. Even if we lived in the same world, there'd come a time when life'd pull us apart. 'S not a reason to avoid people. Even if it's someone you love more than life itself, that time'll come. There's no guarantee you'll even get to say goodbye. But before that happens, you get to be together, right? You can't just waste all that potential for a rewarding relationship!"
Doubles as a Tear Jerker when you know that, whether he knows it or not, Laguna is speaking from experience; he lost both of the women he cared for, and didn't really get to say goodbye to either of them.
Just to really make you start bawling? The background music is "Eyes On Me", the song the first woman he cared for wrote in honor of him.
It has even more impact if you know how the characters are connected - it's one of the few times that Laguna acts as a father to his son.
Kain's contribution in the 12th cycle (see this game's corresponding Awesome tab for the full story), more specifically him going back to help his friends even though Golbez pointed out that he had the chance to escape his own demise. Duodecim goes to great lengths to show that, yes, Kain really is a hero, and he deeply cares about his friends.
It's especially satisfying because at the beginning of Kain's plot arc, the audience reaction was probably "Oh, Kain is a traitor, yawn, we saw that happening already".
At the end of the Warrior of Light's story, when all the Warriors of Cosmos are gathered, the first thing he asks is if everyone's all right. He doesn't ask about the crystals, but about their well being. It's a small touch, but it works.
Prishe's story in Dissidia 012 Duodecim is short but very sweet and very pivotal to the story. Especially when she gives the Warrior a speech about what it is to be a person; they are just so cute together (not in the romantic way).
Speaking of the Warrior of Light, the fact that Cosmos sacrifices herself to save him is very endearing. Especially when you consider that when they first met in Duodecim she hesitated at the idea of making him one of her warriors.
A short one from Duodecim. Gilgamesh's quote when you're playing as Terra is one of these. The Hot-Blooded lug is flirting with most every female in the game. Terra's one of the few exceptions; he asks her what's wrong, and if she wants to talk. Equally funny and heartwarming.
The scene where, heading back to Cosmos, Bartz talks with the Warrior, and suggests getting the others to help think up a name to call him by. While the Warrior turns down the offer, he still thanks Bartz anyway.
Bartz: How about this for an idea? We get everyone to come up with a new name together!
The very first moogle met in the storyline greets Lightning, explains to her what the moogle shops are, and gives a few other tips. You later encounter him at Cornelia, now with his own shop, but all he has to sell are pebbles. Fast forward to Confessions of the Creator — though the inventory depends on the total KP you've earned throughout the game, he sells the rare Elixir items needed for buying trade accessories, some of the best and rarest accessories and summons, and the KP Bonus and Banish/Death skills, two of the most useful map skills. As the saying goes, he made it after all, even if Confessions is All Just a Dream.
Zidane's intro quote to Golbez in Dissidia 012 - "I think you're a good brother, old man". Considering Zidane's relationship with Kuja and Golbez's character arc and main source of internal conflict, very touching.
Near the end of the Epilogue of Light to All in Dissidia 012, Terra wonders about the moogles, since the summoned warriors seem to be their only customers, and that they must really value the KP they spend there. She feels like she should spend more KP before they face Chaos and go home, and wonders if the moogle nearby would let her fluff him. The entire game they've helped you out with skills and items in exchange for the KP you've earned, and now that it's almost over, Terra seems to be the only warrior that spares any thought to what's going to happen to them afterwards.
The moments of friendship between Kain and Tifa in Dissidia 012s story mode. It's just really sweet that even though Tifa's not sure Kain killing the other warriors of Cosmos to save them from the manikins is right, she insists that she knows him and knows he feels what he's doing is right. And she'll stand by him as a loyal friend should.
Tidus beating Jecht at the end of his chapter of Light to All. Finally being able to earn his father's respect and they reconcile. Even better in Shade Impulse when Jecht shows up to give him advice and as he leaves, says that it was fun being his dad.
In the 12th cycle, Jecht performed a Heroic Sacrifice to save Tidus, proving that he still loves his kid, no matter what side of the war he's on.
Even at Shade Impulse, in the very end when he fades, he vanishes in light. At his core, he was always a Warrior of Cosmos.
Comsos tells the Warrior of Light that she must focus all of her remaining energies on keeping the world in balance while he and the others go find their crystals and apologizes for not being able to help them more. Also a bit of a Tear Jerker when you learn of the crystals' true nature and the role they play in her downfall...
Cosmos: Forgive me... I want to be with you... But allow me to rest... Then soon...
Warrior of Light: Cosmos, your radiant light shall always be with us.
Golbez's Shade Impulse ending. Golbez is the only villain who was not actually fought as a boss and therefore doesn't die after his defeat, opting instead to wander the world. As Golbez begins to depart, again claiming he has no right to be near Cecil and that his connection to Chaos was proof of his weak heart, Cecil tells him he will eventually overcome that part of himself someday, asking him to join him when that day comes. Golbez says Cecil is too kindhearted to be a knight, but contemplates the possibility of joining his brother if the light shines upon him.
It's a small scene, near the end of the conflict Garland and Golbez talk about the cycle of battle and what will happen next. While Garland is his usual moody self, Golbez reaches out to him by telling him to try and find hope for the future. Considering how often Golbez has told Cecil he's too far gone to be saved, it's a rather kind gesture.
Golbez: But is that your true desire?
Garland: ...What is your point?
Golbez: The wheel of fate has already began to turn, why not seek a new cycle of hope?
In the first report of 012, Cloud and Kuja are talking about their participation in the conflict. When they part ways, Cloud wishes for Kuja to hang onto the memories he holds dear. Kuja's quick to remind him they aren't friends, but wishes him the same anyway.
While marching to Chaos' citadel, the Warrior of Light opens up to the other warriors and admits that he's starting to worry that while they're all starting to remember their lives and homes. He still hasn't remembered a thing. The others assure him he'll remember his past in time, and this seems to ease his mind. Tidus however waits until he's alone to talk to him, telling him that the memories he's made since all the warriors met are just as important, and shouldn't be forgotten. The warrior agrees, promising to never forget his new friends.
A small one, but during the final chapter of Treachery of the Gods, Yuna expresses her worry about Tidus and Jecht. Though she didn't mention them by name, Tifa and Lightning immediately know who she was thinking about and they both give her the chance to stay behind with them. That was heartwarming by itself, but then Yunastill chooses to go fight with them even though the other two made it clear they would understand if she wanted to back out.
The last time the Warrior of Light and Lighting see each other, before she fades away. Lightning gives him a nod of approval, and a smile.
The brotherly love exchanges between Golbez and Cecil are especially heartwarming.
During side stories and other scenes, Firion notes that he has trouble thinking of a specific reason to fight, unlike everyone else (specifically Cecil wanting to fight/talk to Golbez, and Tidus wanting to fight Jecht). Under questioning, he reveals that his desire is for a world covered in Wild Rosesnote Though he doesn't know it due to memory loss, Wild Rose is the symbol of the resistance movement in his world, and a world covered with them would be free from the tyranny of the Palamecian Empire. He admits that's it's stupid and foolish, the sort of dream a kid would have. Instead of mocking him for it, everyone takes that up as their goal, even Squall. It's a little silly and foolish, but the lengths that everyone is willing to go to support their friend is amazing.