Rome has what must be one of the bloodiest Crowning Moment of Heartwarming possible. Lost and alone since leaving the 13th Legion, becoming a criminal and an assassin before being caught and sentenced to die, Titus Pullo is fighting for his life in the arena. Except he refuses to fight. He just sits there, telling the first three gladiators to kill him and be done with it as they poke him with their weapons... right up until one of them repeatedly insults the 13th Legion. Within seconds, Pullo disarms and kills all three before shouting "Thirteen! Thirteen!", then starts fighting more gladiators as they come out of the gate. Finally he's almost crippled, and about to be killed by the last gladiator. Little does Pullo know, his former commander and new friend Lucius Vorenus is watching in agony, knowing that Pullo (who despite their friendship has given Vorenus more than enough reason to hate him) is about to die. Just as the gladiator seems about to finish Pullo, Vorenus screams "THIRTEEN!" and charges into the arena grabbing a weapon. The last gladiator and Vorenus each wound each other several times until Vorenus slashes the gladiator's leg, and then... ''finishes'' him with his own weapon. Vorenus grabs Pullo and helps him out of the arena, as the crowd and even the arena guards chant "Pullo! Pullo! Pullo!"
Agrippa: I'd tear down the sky, if you wanted me to.
Pullo and Vorenus taking care of each other's children during the years they are apart. Pullo's message to Vorenus to let Vorenus know that he's really in Alexandria with Octavian being "His children are well and I hope my child is well also."
When Caesarion asks Vorenus to tell him about his father Vorenus begins to talk about Caesar but soon slips into telling him about Pullo instead without even realizing it at first.
When Vorenus flees with Caesarion he goes to a place where he hid with Pullo way back in season one and Pullo knows exactly where to find him.
Octavian is a cold an often heartless character but whenever he speaks to or about Pullo or Vorenus he softens and shows clear attachment to them. When Pullo shows up at the battlefield after Octavian has defeated Mark Antony Pullo is looking for Vorenus to tell him that his children are alive. When Octavian hears this he actively helps Pullo find Vorenus even though Vorenus fought for Antony.
Atia helping to arrange a secret meeting between Octavia and Agrippa after their secret romance has been found out. She seems so happy for her daughter.
Seeing Atia with her granddaughter is also very sweet.
Any time we see how much Atia truly does care for her children. The season two episode where Agrippa comes to tell them Octavian has won against Antony she initially thinks he's there to tell them Octavian is dead and she nearly breaks down.
The fact that Vorenus and Pullo stay together, always close to one another, throughout most of the show. Especially in the first season where they dislike each other at first and it takes Vorenus a long time to learn to tolerate Pullo. They are a team long before they grow to love each other as brothers.
Mascius says they are "like Castor and Pollux".
In season two they call each other "brother".
In season one when Vorenus takes a job as a butcher Pullo goes to work with him, just because they're always together.
When Erastes Fulmen threatens Vorenus, Vorenus tells Pullo to hold even though he has his back turned to him. He knew that Pullo would be willing to kill or be killed to help him.
Mark Antony coming to pull Vorenus out of his depression. He looks absolutely disgusted while he's there but he didn't have to come in the first place and he does what he can to get Vorenus back on his feet.
Antony dies with Vorenus at his side (actually Vorenus is the one who kills him, at Antony's request), pulling himself into Vorenus' embrace as he dies.
Vorenus then washes off his makeup and dresses him in his Roman attire so he could be truly Roman in death.
Vorenus saying that it has been an honour serving with Antony, and Antony's touched "has it?".
Atia's slave Castor took in a boy from the streets to be his lover, not knowing that the boy was actually working for Servilia with the goal of poisoning Atia. The attempted murder fails and the boy is tortured then killed by Timon. Castor throws himself at Atia's feet, knowing full well that she has the legal right to do exactly the same thing to him and is most certainly not above doing it. Instead she forgives him instantly and plays it off as a sight annoyance, showing how deeply she does in fact care about her closest slaves.