WARNING: Spoilers for Cobra Kai season 3.
Samantha LaRusso defeats Tory Nichols in Cobra Kai season 2, so why she is so scared of her in Cobra Kai season 3? Portrayed by Mary Mouser, the teenage character is the daughter of co-protagonist Daniel LaRusso (Ralph Macchio), and mostly gets along with everyone at her school. Still, Sam feels the wrath of Tory after an alcohol-influenced mistake, and subsequently has a traumatic life experience during a school brawl.
Cobra Kai season 1 establishes the context for Sam's future mental health issues. She initially begins dating Miguel Diaz (Xolo Maridueña), but struggles to maintain a healthy relationship because her boyfriend is the top student of her father's former rival, Johnny Lawrence (William Zabka). In Cobra Kai season 2, new student Tory begins a romance with her dojo colleague Miguel, and creates friction between Sam and her long-time friend Aisha Robinson (Nichole Brown). After Sam drunkenly kisses her ex-boyfriend Miguel in the Cobra Kai season 2 finale, Tory decides to publicly confront her at school, but ultimately loses the fight. Meanwhile, Miguel ends up in a coma after battling with Robby and falling over a ledge.
In Cobra Kai season 3, the after-effects of the school brawl are felt throughout the San Fernando Valley. All of the participants receive attention because of media exposure, and Daniel nearly loses his car dealership business because of his association with the event. But even though Miguel recovers and returns to school, Sam continuously struggles with anxiety issues, primarily due to the consequences of her drunken behavior. She suffers a major emotional setback after seeing Tory for the first time, and later has a nightmare at the beginning of Cobra Kai season 3, episode 7, "Obstáculos." Later, when Sam quits karate and seems nervous about starting the school year, Daniel decides to spend an afternoon fishing with his daughter, and attempts to figure out what's troubling her after a recent confrontation with Tory.
Sam's anxiety in Cobra Kai season 3 is the result of many experiences. Daniel's daughter naturally feels guilty about what happened to Miguel, but also realizes that she could've been severely injured during the school brawl, or even killed. Whereas the Cobra Kai students live by a "no mercy" mentality, Sam adheres to her father's peaceful practices at Miyagi-Do, which he learned from his Japanese-American mentor, Mr. Miyagi (Pat Morita). During the aforementioned fishing trip in Cobra Kai season 3, Sam opens up to her father about the specifics of her anxieties:
"When the fight started, I... I couldn't move. I couldn't breathe. Felt like... like my heart was going to jump out of my chest. I knew there was something wrong even before then - I just... thought I could handle it... I felt like it would all happen again. Like I would get hurt. And Miguel would fall. And Robby would run. My brain could feel it starting, and so my body just... stopped."
Sam's emotional trauma adds some depth to a narrative that revolves around teenage violence. Both Daniel and Johnny defend their martial arts practices to the community, and believe that karate should be embraced as a viable outlet for kids who feel like they need to defend themselves. Still, there isn't necessarily an in-depth exploration about how violence truly impact the psyches of the young leads. Sure, Sam and her father do indeed bond during the fishing sequence, but it's structurally designed to set up yet another reference to the movie franchise, as Daniel remembers how he didn't lose to fear during the climax of The Karate Kid Part III. And when Sam sees Tory again in Cobra Kai season 3 finale, she initially runs away and ultimately doesn't fully resolve their on-going conflict. Moving forward, Mouser will presumably have a more prominent role, as there is still plenty to address with her character.