In Legend of Korra, the sequel to Avatar the Last Airbender, Mako and his brother Bolin are introduced in the probending team, The Fire Ferrets. Bolin and Mako grew up orphans after a firebender killed their parents. They worked for the Triple Threat Triad before getting a more legitimate life for themselves with probending.
Mako's life changed upon meeting Korra and forming their own team outside of the arena. He is a talented firebender, despite not receiving much training, even harnessing lightning to turn the tide of battle on several occasions. Throughout the series, he has shown his loyalty and protective nature and has more than a few memorable lines.
10 "You're The Avatar And I'm An Idiot."
This is said early on in Season 1, moments after Korra nonchalantly reveals that she is an earthbender and firebender in addition to being a waterbender. Mako, putting the pieces together, says this to which Korra replies, "Both are true." Despite this, it still takes Mako some time to soften up towards Korra. Contrarily, Bolin is amazed by her and even goes as far as to ask her out, but ultimately gets turned down. This is a memorable exchange as it highlights the beginning of Mako, Bolin, and Korra's companionship.
9 "Your Best Friend Is A Polar Bear Dog. Somehow, That Makes Perfect Sense."
A lighter line said with the intent of poking fun at Korra and her quirks, this happens when they first discover Bolin's is nowhere to be found. They take Naga to search for him and assume he got into a messy situation with the Triad, later finding out he was kidnapped.
Without Bolin there to add to the conversations, Mako and Korra are forced to get to know each other a bit more. It is a comical, memorable quote that goes in line with Mako calling Korra crazy earlier on.
8 "We Were Orphans Out On The Street. I Did What I Had To Do To Survive And To Protect My Little Brother."
The line is part of a conversation that Korra and Mako have in between searching for Bolin. Following his revelation that they worked with the Triple Threat Triad, she asked if he was a criminal. He then explained their story a bit more to her, how their parents were mugged and killed and they were left alone to fend for themselves. This scene, despite the circumstances, shows Mako opening up to Korra more so than he had to most in his life as she gets to know him more deeply.
7 "Bolin Is The Only Family I Have Left. If Anything Happened To Him..."
While this is in the same conversation, it is worth mentioning as it provides a first look at the more protective side of Mako. It also shows just how important family means to him and with it, loyalty. In terms of Bolin, Mako was always really protective as he felt he was his responsibility.
With that, it was his responsibility to make sure they always had money or food or whatever they needed to survive. Korra's reassurance to him following this line is also an important step in their relationship.
6 "The Scarf Was My Father's And It's All I Have Left Of Him. I Just Feel Like... Like It Keeps Me Safe."
Early on in their relationship, the first of various romances within Team Avatar, Mako and Asami took a carriage ride around Republic City Park where Asami asked about a scarf she had gotten for Mako. He opened up to her about what happened to his parents and just how much his scarf meant to him. With it, he feels his father's presence as he goes. Asami responds by opening up about the loss of her mother. It is around this time that we see a closeness and deeper connection between the pair.
5 "Looks Like You Had Some Car Trouble. Good Thing The Police Are Here."
Following an epic car chase scene at the start of Season 2, Mako immobilizes the criminals he is pursuing. That is when he utters this line which makes for one of his best moments as well as a strong opening to the season. It shows Mako making a name for himself as a cop using his bending for good catching bad guys right off the bat. This quote is the icing on the cake to an already awesome scene where Mako's proves his prowess as a firebender and as a motorcyclist.
4 "I Broke Up With The Avatar."
Following Mako telling the President that Korra planned to get the military for the North-South water tribe conflict, she storms into his office. She claims he betrayed her and her whole family by telling him.
This results in Mako breaking up with her since they are prioritizing their jobs above their relationship. Loyalty is what Mako is known for, yet he initially struggles with where his loyalties lie. Aside from the sad tone of the scene, it is iconic as few people can say they broke up with the Avatar.
3 "I'm Sure They Would Want You To Have This."
While this line seems simple, the context and implication are anything but. When Team Avatar journeys to the Earth Kingdom in search of airbenders imprisoned within, Mako and Bolin meet their family. It is an emotional reunion as they inform everyone about the loss of their parents. Their grandmother is especially saddened that she never saw her son again or met his wife. Upon uttering this line, Mako gives his dad's scarf to her as something to remember him by. This is especially touching given how much that scarf meant to Mako growing up.
2 "I Don't Have Time To Argue! I'm Doing This So Get Out of Here!"
In the epic finale of Season 4, Mako finds himself playing the hero once more in a huge way. After Bolin and Mako attempt to disable Kuvira's giant mecha using levers, they are forced to explore other options. After Bolin reveals the explosive nature of the vines powering the Colossus, Mako knows what he must do. Telling Bolin to get the others and leave, he uses his lightning to blow up the vines, thus destroying Kuvira's mecha. His arm burned and left unconscious, his brother saves him in the nick of time.
1 "I'll Follow You Into Battle No Matter How Crazy Things Get. I've Got Your Back And I Always Will."
Following the battle and the defeat of Kuvira, Korra and the team regroup near the newly formed spirit portal. Korra goes up to Mako, who has his injured arm in a sling, struggling to find the words to express her gratitude for all he has done. He responds with the quote seen above, reassuring her that he is always there for her, making for a fitting last interaction. Despite their on and off relationship, this shows how Mako loves Korra, regards her as family and what that means to him.