Furies of Calderon: Half-drowned and injured, lost in the middle of a strange and hostile forest, having just taken a beating at the hands of the local holders, and on a very dangerous mission for a very dangerous person, Aldrik ex Gladius's first priority is finding out where Odiana is. She's insane, he's ruthless, and they actively work to hurt and undermine the Realm and its people, but you can't deny that they love each other.
Tavi promising Kitai that she'll never be alone at the end of the book. Referenced again much later, in an exchange where Isana mentions that, since she's the only Marat without a clan, it must be terrible to be alone... "I would not know. I am not alone."
While travelling to Aricholt, Amara avoids Bernard because she can't bear children and doesn't want him to get more attached to her. Doroga asks her if Bernard has 'eaten the wrong soup' (describing an incident shortly after he and his wife were mated, when he praised soup that she had not in fact made). When Amara explains that there are other factors making their marriage impossible, Doroga simply tells her that what she and Bernard have is too precious to let anything else get in the way.
Amara manages to convince Rook to turn on Kalarus not through bribes or torture, but by doing what's right: the moment she learns of Masha being held hostage by Kalarus, she offers to rescue the child. Rook's response is to break down crying as she's presented a way out of the horrible scenario that's kept her leashed to Kalarus. What makes the scene even more powerful is that Invidia is watching the whole thing, and being Invidia, she doesn't seem to understand what just happened.
When Max reminds Tavi how much he's accomplished without any furycrafting, with the result that the whole legion believes in him and is willing to fight rather than run from the impossible odds they're facing.
Captain Cyril demonstrates that he's A Father to His Men by keeping Max's Wicked Stepmother from causing him an "accident" and arranging for Tavi to stand guard over him - and while Tavi's getting ready, Cyril stands guard for Max.
When Crassus and Maximus finally take the field together—they're brothers with a rough past at the best of times, but spend a lot of the book getting closer to one another, culminating in the opening of the final battle scene, where they move in perfect unison and coordination, just as they were always meant to.
During the epilogue, when Amara and Bernard discharge a High Lady's debt to them by asking that the redeemed spy and her daughter be given a quiet place to live. Oh, and ponies. Of course that only makes the part in the fifth book when the Vord Queen causally murders that same redeemed spy out of hand all the more heartbreaking. But it comes back to heartwarming again when Bernard and Amara have adopted the little girl... And are giving her pony-riding lessons. In the middle of the Apocalypse.
The very last scene, when Tavi finally comes into his furies. He's just so gleeful about being able to use a simple lamp that you can't help but grin.
Mistress Cymnea taking in "Gerta," who she believes is a young blind vagabond, into her care. And when the battle comes to the First Aleran, she asks Tavi if he has seen "Gerta". She doesn't realize "Getra" is a disguised Kitai.
Captain's Fury: Tavi reveals to Isana that he knows about his parentage, and she finally tells him the whole story, ending with Tavi shocked and angry at the years of lying, but also still as full of love for her as ever.
Araris asks Isana if she will marry him—and she accepts the proposal. Overlaps into Crowning Moment of Funny, even cracking them both up In-Universe because he does it while they're tied up together in a tent with sacks over their heads, held hostage by Senator Arnos's thugs.
After the destruction of Kalare, Tavi is the only person who isn't all 'you horrible person how could you do such an awful thing!' but quietly asks Gaius if he is all right because he's seen first-hand, in Academ's Fury, just how important keeping his people safe is to Gaius.
Princeps' Fury: When the surviving Narashan Canim are freed from Lararl, and they turn out to be mostly the wives and children of the Canim with Tavi. Oh, and among them is Varg's/Nasaug's daughter-in-law/wife, and their grandchildren/children. After four solid books of Varg being a huge, menacing beast who growls everything he says and who can and does break buildings with his bare hands, it's a wonderful shock to see him to running over and be mobbed by happily-squealing pups and play wrestling with them.
First Lord's Fury:
Kitai and now Tribune Cymnea have maintained their friendship. It's likely Kitai spoke to her about being pregnant.
When Tavi realizes Kitai is pregnant. She is worried about how he'll receive the news and he tells her, in no uncertain terms, that he doesn't give a damn what anybody thinks. It's their child, no matter what. And the scene ramps up the heartwarming by ending with Tavi helping Kitai to feel their baby's presence through his watercraft.
During the final battle at Calderon Valley, Lord Riva speaks with Bernard, and admits that they have both been at odds for so long, when they needed to worry about the real threat of the Vord. He then apologizes and offers whatever help he can, and Bernard accepts, shaking his hand. Small bit, but wonderful.
Tavi's conversation with Fidelias, just before his wedding. Fidelias remains in his Death SeekerAtoner phase, and wants to die for his treason. Tavi's punishment? He sentences Fidelias ex Cursori to death... but Valiar Marcus will train the next generation of Cursors, and will enjoy the respect and admiration he's gained from his past and present Moments of Awesome: in short, he's been born again and given a second chance.
Tavi's message to all of Alera. After the Vord Queen gave a powerful "Resistance is Futile" speech, he gives a counter, that he is back, that he will lead the armies against the Vord, and will rout them from their lands. But it isn't just that, he understands those civilians who are starving are cut off from supplies, and so grants them permission to accept the clemency of the Vord if it is to save their lives. However, any "Citizen" who does this is a traitor, for too long have they taken from those "beneath their station" and now it is time to pay back what was taken. Even his political enemies are impressed by this. And made all the better is this message was a distraction to allow his men to rescue captured holders being held by the Vord Queen by awakening the sentries and giving them a chance to see what's there.
Tavi's wedding to Kitai. Also, their son Desiderius.