At his empire's height, Vecna was betrayed and destroyed by his most trusted lieutenant, a vampire called Kas the Bloody-Handed, using a magical sword that Vecna himself had crafted for him, now known as the Sword of Kas.
Stranger Things season 4 already showed audiences how Eleven can defeat Vecna in the Netflix series' final season.
The trio gets upstairs and find Vecna strung up on his vines, unconscious while he deals with Eleven in the mind palace. They torch him with Molotov cocktails, and when he wakes up, Nancy shoots him with a sawed-off shotgun.
Nancy, Steve and Robin get freed too. They rush to find Vecna's body and burn it down. With this Vecna's soul turns to ash in front of Eleven. Max's dies in Lucas' arms, thus getting Vecna his fourth kill.
note: This post contains spoilers for the end of Stranger Things 4 part 2.] In the battle against Vecna, Max dies. But Eleven — and the power of love — brings her back.
Through the window, Max saw her real body levitating above the cemetery, her friends panicking on the ground below. Bracing herself, Max pulled at a vine in Vecna's neck, causing him to writhe in pain and accidentally release her from the vines' grasp.
In what essentially amounts to a straightforward revenge thriller, Murphy (Perry Mattfeld) vows vengeance at Max (Casey Deidrick)'s funeral. She finds out that it was Josh (Theodore Bhat) who called off the deal and caused Max's death.
Eleven has a memory during this episode and realizes that 001/Henry Creel (Jamie Campbell Bower) wants her to join him on his evil journey, and she banished him to the Upside Down. 001 then transformed into Vecna, the horrifying Stranger Things villain.
As the ending of Stranger Things season 4, part 2 made very clear, Vecna, a.k.a. Number One, is far from finished with Hawkins. Yes, he may have been beaten and battered by Eleven, Nancy, Robin and Steve, but he did survive.
Ultimately, it is revealed in Stranger Things season 4's finale that the reason why Vecna was killing Hawkins teenagers was to create a massive gate that merges the Right Side Up with the Upside Down - and he specifically needed four bodies to do so.
Vecna's first big credited kill was Chrissy Cunningham (Grace Van Dien). He followed that murder with canonically terrible driver Fred Benson (Logan Riley Bruner) and basketball star Patrick McKinney (Myles Truitt).
His main weakness is not any particular set of traits, but a constraint imposed by his location: the Chaotic Quest entrance is a portal rather than a staircase, and Vecna is covetous. Vecna will therefore readily warp to you, but will not teleport away to heal.
After inflicting protracted suffering, Vecna finally executes the victim, using his powers to make them levitate before snapping their limbs and gouging out their eyes.
Eleven was able to overpower Vecna once Mike explained how much he loved her, suggesting she truly did have enough strength to kill Vecna, but the encouragement came too late.
There's been debate as to whether or not this scene implies that Eleven created the Upside Down or merely opened the first gate to it. But according to Millie Bobby Brown, the Upside Down existed before El ever meddled with it. “I don't think that she created the Upside Down,” Brown told Variety in June.
After many years of loyal service to Vecna, Kas eventually betrayed his master. It is said that the sword itself whispered to Kas, convincing him to slay his master and usurp his power. The battle destroyed Vecna's Rotting Tower, and cost the lich his left hand and eye.
Is Max alive at the end of Season 4? Physically, yes. Lucas tells his friends that Max is in a coma, and we see her wearing casts on her arms and legs. The Duffer brothers have also confirmed that at the end of Season 4, Max is alive yet "brain dead, blind, and all of her bones are broken."
If the eyes and the right hand weren't enough to convince you already, it's confirmed that Vecna was once human – and he has a very strong connection to Eleven and the Hawkins Lab.
Did Eddie Munson Die? According to the Duffer brothers, yes.
Sharing more about Eleven's real father Andrew Rich could be a great way to wrap up the story.
What does Vecna want with El? In his twisted mind, Vecna believes that he his helping the world by wiping out humans, as a "predator, but for good." When Vecna asks for El to join him, it's because he also sees her as a predator, "better" than humans.
Following Eleven's resistance, Vecna sought after Eleven's 'power', which he identified as "a means to open [his] own doors" (gates).
Max (Casey Deidrick) dies in the penultimate episode of In the Dark, and it's one of the worst decisions the series ever made. Max gets shot while escaping into the elevator after saving Murphy from the fundraiser scheme as it goes wrong.
1. Perry Mattfeld is not actually visually impaired. Although the show's main character Murphy Mason is blind, the actress who plays her, Perry Mattfeld, is not.
He was engaged to Murphy Mason before his death in S4 E12.