The following contains spoilers from Star Wars: Darth Vader #22, on sale now from Marvel Comics.
Subtlety is not a huge part of the Star Wars universe. To that effect, undercover operations are few and far between, but there are a few noteworthy operatives in the franchise. Emperor Palpatine would probably be the best example -- since he spent nearly two decades pretending to not be a Sith. Jedi Master Quinlan Vos also spent a lot of time undercover, and Obi-Wan Kenobi did the same when he posed as bounty hunter Rako Hardeen in Season 4 of The Clone Wars.
Hopefully, Star Wars: Andor will give fans more undercover, secret spy genre motifs. For now, though, fans will have to be satisfied with Darth Vader's lackluster attempt at undercover work in Star Wars: Darth Vader #22 by (by Greg Pack, Raffaele Ienco, Alex Sinclair, and VC's Joe Caramagna).
Following the War of the Bounty Hunters, it was clear that Qi'ra had built Crimson Dawn to much more than a crime syndicate. She had operatives all over the galaxy, who had infiltrated everything from the Rebellion to the Imperial bureaucracy. Because of that, Palpatine sent Vader on a mission to uncover and eradicate every last member of Crimson Dawn.
While on that mission, Vader employed Ochi of Bestoon (who's been trying to play both sides), a litany of other assassins and a number of local heroes who took issue with Crimson Dawn's methods. However, the most noteworthy person that Vader encountered was Sabe (one of Padme's former handmaidens). She has tried to kill the Dark Lord a few different times. This time, however, Sabe tried something new. She used Vader and influenced him kill a bunch of Imperials by planting a fake list of Crimson Dawn operatives.
As the most recent storyline opens, Vader had Sabe and Ochi with him, and the Sith Lord wanted to teach them both a lesson. Using some Hydra-like monsters, he showed them that the only way to win was by making their enemies fight amongst themselves, otherwise they would only multiply. That's when the undercover work happened on two fronts.
Darth Vader "joined" Crimson Dawn and used Sabe's information to set them up. Arriving at designated drop zone, Sabe emerged from their shuttle and claimed trhat Vader was in charge fo the Crimson Dawn cell. Of course, Vader is a recognizable galactic figure, and no one bought it. Everyone recognized him as Palpatine's muscle and immediately opened fire. Vader and Sabe killed all of them without hesitation, thus completing step one of the subterfuge -- make Crimson Dawn angry at the Empire.
Meanwhile, Vader sent Ochi of Bestoon to rile up General Romodi. Saying that Vader had gone rogue and joined Crimson Dawn, he convinced the general that he needed to make a move. So, Romodi sent his troops to attack "Vader's Crimson Dawn cell." What ensued was a battle between the Imperials and Crimson Dawn that ended with everyone dead.
All in all, Vader's undercover stint worked for all of a few seconds, but it was still effective because he got what he wanted. Crimson Dawn was decimated in that sector, and he made sure Romodi knew his place. It will be interesting to see what Vader does next because Sabe revealed that she knew his identity as Anakin Skywalker. On top of that, the Crimson Reign mini-series will be ending soon. Vader and Qi'ra's next meetying will be interesting and probably deadly.