Imperial Inquisitors serve the Sith, devoted to hunting down survivors of their old religion. Some of the Inquisitors are Order 66 survivors themselves, captured and tortured by the Empire until falling to the dark side. Others had already lost their way, either willingly leaving the Jedi Order or being cast out before Darth Sidious had the rest were wiped out.
Introduced in canon in Star Wars Rebels, the Grand Inquisitor answers directly to Darth Vader. The other Inquisitors, known as Brothers and Sisters, obey the Grand Inquisitor, though there's a fair amount of in-fighting and backstabbing to earn the favor of their master. Only the Third Sister, Reva, knows the true identity of Vader, and even she underestimates his power. Darth Vader is regarded as the pillar excellence for Force s and lightsaber wielders, but do the Inquisitors possess the skills to rival him?
The Inquisitors' Force Powers Compared To Darth Vader
The Inquisitors' power in the Force varies by the individual. While the Grand Inquisitor is the strongest of the group, others, like the Tenth Brother, are considerably weaker. Vader and Sidious deliberately didn't teach the Inquisitors the true ways of the Sith, as their servants may then have truly become threats. The Inquisitors are more than equipped to deal with surviving Jedi Padawans, who themselves haven't developed their Force powers, but the dark siders are easily outclassed by the likes of Obi-Wan Kenobi, Ahsoka Tano, and Darth Maul.
Darth Vader, by contrast, is arguably the most powerful being to ever exist. Created by the Force itself, Vader performed unfathomable feats as both a Jedi and Sith, things the Inquisitors were simply incapable of. Reva spent years ascending the ranks to take revenge on Vader for slaughtering her fellow Jedi younglings, but when the time came to make her move, he only needed to lift a hand. There are few who can stave off lightsaber attacks with Force maneuvers and pull ships out of the sky, but Vader did so with ease.
The Inquisitors' Lightsaber Skills Compared To Darth Vader
Unlike the Force, the Inquisitors are given much more training in lightsaber combat. When Vader was first introduced to his servants, he took a lumb from each to teach them loss. That served as a motivator for their lightsaber training, which was generally adequate to defeat hunted Jedi. Fortress Inquisitorius has a chamber holding the remains of just a sampling of Jedi who were successfully killed, giving credit to the hunters' skills. Most of them were eventually dispatched by other Force s, however, with Cal Kestis defeating the Second Sister, Kanan Jarrus besting the Grand Inquisitor, Ahsoka Tano making the Fifth Brother and Seventh Sister look silly, and Darth Maul killing the latter two off quickly.
Vader was one of the best lightsaber duelists of his time, becoming even better in combat than he was as Jedi Anakin Skywalker. He was only truly beaten by Obi-Wan Kenobi, who was able to take advantage of his arrogance and hatred and use them against him. For a gauge on where the Inquisitors stand relative to Vader as duelists, look no further than how he fared against the opponents that beat them. Cal was forced to flee from Vader, while Kanan and his apprentice Ezra Bridger were easily beaten. Maul fears Vader, indicating there's an untold conflict that transpired between the two, and Ahsoka was the only one to hold her own - and even she was dead, if not for an unprecedented save.
Could The Inquisitors Ever Beat Darth Vader?
Under no circumstance could the Inquisitors ever defeat Darth Vader, individually or as a group. The Sith Lord is far too powerful, a dominant presence in the Force who could kill them all without a lightsaber. What Vader did to Reva would be multiplied by a dozen, and it would be easy to accept. As a Sith, Vader is trained to twist his pain and anger into strength, fueled by his hatred. The Inquisitors were always meant to be disposable lackeys in Star Wars, and any attack on Vader would result in a prompt slaughter.