After being tasked with assassinating her, Daario sneaks into Daenerys's private pavilion dressed as one of her Unsullied soldiers (it's unknown whether he killed an Unsullied or just stole the armor from somewhere):

Daario then tells Daenerys that he was sent to kill her but he doesn't want to. She asks him what his captains would have to say about that, and he replies that she should ask them herself, showing her this little surprise:

Daario, Jorah Mormont and Grey Worm sneak into Yunkai through a small gate in the back of the city in order to open the main gates so Daenerys's army can charge in and conquer the city. The two guards stationed at that small gate recognized Daario and let him in, but then Daario killed them to clear the way for Jorah and Grey Worm (off screen though):

Inside the city, they are confronted by a large group of soldiers. The three warriors dispatch them with ease despite being heavily outnumbered, and Daario himself does very well:

At one point he blocks a strike from an enemy who is behind him and then proceeds to kill him:

When arriving in Meereen, Daenerys and her army find the city ready for a siege. Suddenly, the city's main gate opens and a lone rider emerges - a champion of Meereen who challenges Daenerys to send forth a champion of her own to face him in single combat, shouting taunts and insults at her army and even urinating at their direction. Daario volunteers to fight the Champion of Meereen and steps forward to face him. The champion rides at Daario in full gallop, lance in hand, while Daario just stands there. He then pulls out his dagger, waits for the right moment, throws it right at the horse's eye and beheads the now horseless champion with his arakh:

Daario tells Daenerys of the skills and fighting styles that he mastered in his days as a pit-fighter and of his fame and renown:

Daario has knowledge on military tactics and strategy. After Ser Barristan Selmy is killed by the Sons of the Harpy, he suggests retreating to the Great Pyramid and use it as a base of operations, and send units of soldiers to systematically cleanse the entire city of Sons of the Harpy:

Daenerys decides to marry Hizdahr zo Loraq and reopen the fighting pits in order to try and create peace in Meereen. However, shortly after the games in Daznak's Great Pit start, tons of Sons of the Harpy swarm the arena and start slaughtering people by the dozens, with their main target of course being Daenerys. In the skirmish that ensues, Daario slaughters many Sons of the Harpy himself:

Throws his dagger right at a man's heart:

In Daenerys's absence, the slave masters of Yunkai and Astapor sailed their fleets to Meereen to commence an assault on the city and Daenerys's army, while the Sons of the Harpy killed more civilians. Daenerys comes back to the city and unleashes her dragons against the attackers, while Daario leads her new Khalasar in an assault on the other side of the city:

When Daenerys and her army prepare to leave Yunkai and head for Meereen, Daenerys notices that Daario and Grey Worm are absent from her entourage. She finds them at the back of the army, sitting on the ground facing each other, each holding his sword with his arms stretched forward. They were gambling to see who breaks first, with the victor having the honor of riding at Daenerys's side on the road to Meereen. Missandei tells Daenerys that they were at it since midnight, and judging by how the sky looks, they were holding their swords like that for at least 7 hours straight if not more. And they both looked perfectly OK too. This feat might not look like much in the beginning but it's actually very impressive:

This next one should be taken with a grain of salt. Daenerys climbs into her private chambers and is surprised to find Daario there. She asks him how he got there and he responds that he climbed through the window. So far so good, pretty impressive but nothing too unusual. He then hands her a banquet of flowers and tells her this:

When searching Meereen for Sons of the Harpy, Daario, Grey Worm and a few Unsullied reach a house that was seemingly empty. Daario then takes out his knife and stabs through a wall, revealing a man hiding behind it. Not too impressive as a strength feat, but it's something:

During the skirmish in Daznak's Great Pit, Daario sweeps his arakh at the calf of one of the Sons of the Harpy with such force that the man is thrown up in the air almost as high as Daario's head. It's a great strength feat that's very easy to miss:

After the skirmish at Daznak's Great Pit, Daenerys flies away on Drogon's back. Jorah and Daario go on an expedition to rescue her and track her path to Vaes Dothrak. They enter the city under the guise of two merchants, however they arouse the suspicion two Dothraki men and a fight starts. Daario outruns and catches one of the two Dothraki, and then breaks his neck:

His motives are simple:

His agenda is simple:

Here he explains why he refuses to lay with whores (or rather, refuses to pay them):

Daenerys decides to stay in Meereen and rule it, and tasks the Second Sons with patrolling the streets and keeping the peace. But Daario hates doing nothing. He has to have something to keep him occupied, preferably a fight. So he asks Daenerys for it:

He speaks how he wants to whoever he wants:

He particularly enjoys yanking Jorah's chain:

Daario doesn't care for power and glory. He cares for things that make him happy, like Daenerys:

To Mero and Prendahl na Ghzen:

"The gods gave men two gifts to entertain ourselves before we die: the thrill of f***ing a woman who wants to be f***ed, and the thrill of killing a man who wants to kill you."

To Daenerys:

"They ordered me to murder you. I told them I preferred not to. They told me I had no choice. I told them I am Daario Naharis - I always have a choice. They drew their swords, and I drew mine."

To Jorah:

"You have a very suspicious mind. In my experience, only dishonest people think this way."

To Grey Worm (spoken in High Valyrian):

Grey Worm: "You are not a smart man, Daario Naharis."

Daario: "I'd rather have no brains and two balls."

To Daenerys:

Daenerys: "Are you sure you don't want a horse?"

Daario: "Why would I want a horse?"

Daenerys: "Horses are faster than men."

Daario: "Horses are dumber than men."

To Daenerys:

Daario: "The Second Sons took the Meereenese navy."

Daenerys: "Who told you to take their navy?"

Daario: "No one."

Daenerys: "So... why did you do it?"

Daario: "I heard you like ships."

To Hizdahr zo Loraq:

"The big men were always too slow to stop my dagger from going where their muscles weren't. Yes, whenever I saw a beast like that one standing across from me, making his beast faces, I knew I could rest easy."

To Tyrion, Missandei and Grey Worm:

"The queen's closest confidante, the commander of the Unsullied, and a foreign dwarf with a scarred face. Good fortune my friends. Meereen is ancient and glorious. Try not to ruin her."

To Jorah:

"Oh, I don't want to fight you, Jorah the Andal. What do I have to gain? If I win, I'm the shit who killed an old man. If I lose, I'm the shit who was killed by an old man."

To Daenerys:

"I pity the lords of Westeros. They have no idea what's coming for them."

Jorah, Daario and Grey Worm VS Yunkish soldiers

Daario VS the Champion of Meereen

Daario in Daznak's Great Pit (against the Sons of the Harpy)

Daario and Jorah VS Dothraki