[s2 spoilers] How did Caitlyn and Mel beat Ambessa? They learned it from Ambessa herself

Caitlyn and Mel leveraged Ambessa’s own Noxian teaching principles against her to win - and it's why Ambessa acknowledges that Mel has indeed become a true wolf.

During Caitlyn and Ambessa’s training session in episode 6, Ambessa teaches Cait the three core Noxian combat principles: vision, might, and guile + sacrifice, which Ambessa proposes as a fourth principle. Mel and Cait embody them all during their fight.

Vision - The girls had a plan. It is evident that Mel and Caitlyn discussed ahead of time how to take down Ambessa, even though the fight didn’t begin the way they likely intended it to (i.e. Maddie betraying Cait and her squad). How do we know this? Cait targets Ambessa’s protective runes, which Mel knew were in Ambessa’s possession after Rictus’s death and Caitlyn knew the purpose of, as Ambessa is shown heating them up during Mel’s conversation with her in s2 ep 8. After she disarms Ambessa, she yells to Mel “Now!”, in which Mel reveals her Black Rose necklace and gives Ambessa over to them, before obviously shutting the Black Rose down to cradle her mother’s dying body. The girls planned this attack and stuck to said plan no matter what, they knew what to do and never lost sight of it.

Might - They achieve this in multiple ways; One, after the reveal that Viktor isn’t in his cocoon thingy, Mel and Caitlyn (who is behind Ambessa and Ambessa is aware of her presence) make eye contact so that Mel knows to distract her mother just enough that Caitlyn can get the upper hand and deck her lol. Caitlyn makes use of her excellent speed, something Ambessa pointed out to her in their training session. Two, Mel physically bends the environment, another earlier comment from Ambessa, to her will via her protective force fields to give Caitlyn and her some relief from Ambessa’s extreme force. They also split up and attack from opposing sides during the hand-to-hand combat sections, forcing Ambessa to monitor all her surroundings, while they only have to focus on the one in front of them. 

However, remember that comment Caitlyn made during the training session when discussing Might? “Too much force exposes you to risk”. Once Ambessa gets the blade near Caitlyn’s face, Mel activates a protective field that pushes Ambessa to focus all her energy into forcing the blade through the field and into Cait’s eye. This places Ambessa in a vulnerable, risky position and Cait is able to snatch the protective runes wrapped around her arm off while Ambessa is distracted.

Guile - Mel’s collaboration with the Black Rose completely throws Ambessa off guard. Mel’s prior conversations with Ambessa lead her to believe that Mel wants nothing to do with them since they killed Kino, and as we know now, she very much does not. However, Mel knows that the smartest path to win is to play both sides - absent honor, absent accountability. 

Sacrifice - Pretty simple. Mel sacrifices her mother and her life in Piltover to save her city. She knows the second her mother dies, she will become leader of House Medarda and be forced to return home to Noxus. Caitlyn sacrifices her eye to grab Ambessa’s protective runes. She was actually holding up pretty well against Ambessa’s might with the help of Mel’s protective field, but she makes the choice to sacrifice her eye in order to completely expose Ambessa to magic. 

This is why Ambessa dies with a smile. She finally believes that Mel is ready to inherit House Medarda. She understood and embodied the Noxian principles. She had no mercy, made the necessary decisions to keep those she cared about safe, and understood that Ambessa was safer as her enemy. What Mel understands that Ambessa never did is that a true wolf knows when to be a fox, something I hope we get to see more of in the eventual Noxian spin-off we’ll be getting.