Star Warshas turned Order 66 intoDarth Vader’s lifelong mission. The first seeds of Order 66 were planted all the way back in 1977, when Obi-Wan Kenobi told Luke Skywalker that Darth Vader betrayed the Jedi Order, helping the Empire hunt down and destroy the Jedi Knights. We didn’t get to see how this played out until 2005’sStar Wars: Episode III - Revenge of the Sith, which revealed the dark truth.
Viewers watched in horror as Palpatine initiatedOrder 66, and the clones turned on the Jedi at his command. Darth Vader played a key role in apparent fulfillment of Obi-Wan’s words; he launched a direct attack on theCoruscant Jedi Temple, and even slaughtered younglings. But since, then,Star Warshas gradually expanded both Darth Vader’s role and the nature of Order 66, turning it into the Sith Lord’s lifelong mission.

Order 66 Was Far More Than Just A One-Time Event
Let’s head toCrimson Reign#3, by Charles Soule and Steven Cummings, which tells the backstory of an expert in the dark side who suffered because of Order 66. Formerly a lecturer at the University of Bar’leth, an expert in the dark side of the Force, her employment had dried up because the Empire didn’t want her knowledge shared. She got in trouble for possessing “illegal contraband” under “Order 66 Codicil Nine.”
What does this mean? Simply thatOrder 66 wasn’t just a command given to the clone troopers.It was subsequently given legal force, branding Jedi and likely many other Force-traditions illegal. A codicil is a legal amendment, so this also indicates that Order 66 expanded over time, encompassing far more than just the Jedi. Still, they would remain Darth Vader’s focus.

Darth Vader’s Inquisitors Enforced Order 66
DisneyStar Warshas placed Darth Vader at the head of theImperial Inquisitors, a group of corrupted former Jedi who hunt down and kill their old brethren.This is the literal fulfillment of Obi-Wan’s first allusion to Order 66 inA New Hope, because he says that Darth Vader helped the Empire hunt down and destroy the Jedi - and the Empire didn’t form until a little while after Palpatine issued Order 66. Vader established his base in the Mustafar system, with the Inquisitors based there too.
This, it seems, wasDarth Vader’s premiere role so far as the Empire was concerned: he was the one who hunted the Jedi. Whenever there were hints of Jedi activity, a report went to the Inquisitors, who were sent out to take them down - either killing them or capturing them so they could be broken. Darth Vader stepped in when the Inquisitors were out of their depth, as seen inObi-Wan KenobiandStar Wars Rebels.
Kylo Ren Believed Order 66 Was Darth Vader’s Lifelong Mission
Now let’s spin ahead to theStar Warssequel trilogy, which introduced Kylo Ren as the primary Darth Vader wannabe. In one striking scene, Kylo Ren stared down at his grandfather’s helmet and prayed to it that he would be empowered to “finish what you started.” It was an odd comment, and it’s only now becoming clear what he meant - because we now know thatKylo Ren will pursue Order 66 survivors in Charles Soule’s upcoming comic book miniseries. He seems to have believed he was continuing Darth Vader’s mission - to destroy the Jedi.
This is only Kylo Ren, of course, and his understanding of Darth Vader was far from complete; he seems to have considered his redemption to be an aberration, rather than the fulfillment of his true mission. Still, the implication is a fascinating one, and it corresponds to so much of what we’ve seen in theStar Warscanon. To Kylo Ren, Darth Vader was the Jedi killer.
It makes a grim kind of sense. Anakin’s fall to the dark side was sealed when he killed Mace Windu, and his first act as Darth Vader was to lead the attack on the Jedi Temple on Coruscant. He became the leader of the Empire’s Jedi hunters, scouring the galaxy forOrder 66 survivorsand doing his best to extinguish the light of the Jedi. It’s easy to understand why Darth Vader’s quest to kill the Jedi came to define him, explaining everything he stood for as the Dark Lord of the Sith.