Why Kylo Ren Can't Use Force Lightning In Star Wars
The sequel trilogy of "Star Wars" films, including "The Force Awakens," "The Last Jedi," and "The Rise of Skywalker," brought back many of the beloved characters from the original trilogy of "A New Hope," "The Empire Strikes Back," and "Return of the Jedi." However, the sequel trilogy also introduced fans to a brand new set of main characters, focusing on what is revealed to be a dyad relationship within the Force between Rey (Daisy Ridley) and Kylo Ren aka Ben Solo (Adam Driver). Both Kylo and Rey are shown to be incredibly powerful Force wielders on their own by the time "The Rise of Skywalker" came around.
For Rey, it is revealed that she is a Palpatine, the granddaughter of Darth Sidious (Ian McDiarmid) himself, which explains much about her abilities. In Kylo's case, he is a Skywalker through Leia Organa (Carrie Fisher), the daughter of Anakin Skywalker (Hayden Christensen), aka Darth Vader. Kylo's power is shown in many instances of the course of the sequel trilogy, including stopping Poe Dameron's (Oscar Isaac) blaster fire mid-shot, deceiving and killing Supreme Leader Snoke (Andy Serkis), and killing all The Knights of Ren after returning to the Light Side of the Force.
However, for Rey, the extent of her powers is only truly revealed during the events of "The Rise of Skywalker." In one particular scene, she accidentally summons Force lightning when trying to save Chewbacca (Joonas Suotamo) from capture. This is an incredibly advanced skill for any Dark Side user. This begs the question: if Rey was able to summon it by accident, why do we never see Kylo use it?
It's likely Kylo never learned how to summon Force Lightning
From what we learned from the Marvel Comics story on Kylo Ren and his upbringing, along with the information explained and even alluded to in the sequel trilogy — it's entirely likely that Kylo never completely learned how to harness Force lightning. During his training from Luke, it was clear that Kylo was the most powerful Padawan at the new Jedi Temple, and when Luke attempted to kill Kylo out of fear of what he might become, Kylo destroyed it and fell to the manipulation of Supreme Leader Snoke (Darth Sidious). Snoke/Sidious wanted to use Kylo as a powerful pawn in the same way as he used his grandfather, Anakin. He would teach and tell Kylo only what he wanted to, making sure that he stayed within limits and would certainly never get to the point of almost destroying him as Anakin did — therefore neglecting training in Force lightning.
As we know, a long time ago the Sith culture decreed that they may only appear in pairs of two, a master and an apprentice. Ultimately, one kills the other for power and control per the Sith way. Sidious has always made it his goal to keep his place in power, making his purposeful neglect of teaching the Force lightning that he has used on multiple occasions highly likely.
Kylo could have not used it to honor Darth Vader
It is very important to also note that Darth Vader does not use Force lightning, and that is not because he refused to or didn't know how to do it — but rather that it would kill him due to his injuries. During Anakin's duel with Obi-Wan Kenobi (Ewan McGregor) on Mustafar in "Revenge of the Sith," Obi-Wan ended up severing Anakin's arms and legs and Anakin was then nearly burned alive, requiring a robotic sort of suit to even live. Using Force lightning could short circuit his life support systems, which is why Palpatine's lightning in "Return of the Jedi" ultimately kills him. "The Force Awakens" shows us a Kylo Ren who is obsessed with following in his grandfather's footsteps, therefore making it possible that he could have used Force lightning but chose not to in an effort to be more like his grandfather.
However, this possibility seems more unlikely as Kylo becomes more distant from wanting to be like Darth Vader throughout "The Last Jedi" and "The Rise of Skywalker." Ironically, Kylo is almost exactly like his grandfather at the end of his journey, returning to the Light Side and saving the one he loves: Rey.
But why could Rey use it without learning, especially if Kylo and she are a Force dyad?
Ultimately, these questions beg the even more interesting one: how was Rey actually able to summon this Force lightning by accident in the first place? It's most likely strictly due to something with heritage, as it is often emphasized in "Star Wars." Being a Palpatine, Rey likely already has some kind of genetic predisposition to Force lightning given how much Sidious used it. Given that we don't know much about her parents or if they even used their predispositions to the Force, it was probably passed down continuously. However, given Kylo and Rey's immensely powerful connection as a Force dyad, it is surprising that Kylo would not be able to summon Force lightning accidentally either. Maybe he can, it could be possible, although he has no lineage of Force lightning users.
Either way, we likely will never be able to confirm the exact reasoning as to why Kylo can't or won't use Force lightning, especially seeing as he returned to the Light Side, whose users never tap into that ability — and the fact that he is now dead. However, it will be interesting to see if or when Rey reappears, and whether that Force lightning will reappear intentionally or accidentally once more.