Star Wars: The Clone Wars season 7 strongly suggests Darth Maul had figured out Anakin Skywalker's fate. He had deduced Darth Sidious' plans, realizing the Emperor's goal was to seduce Anakin Skywalker to the dark side.
Maul always knew. He figured it out before everyone else. He even staged a massive war on Mandalore with the sole intention of luring Anakin and Obi-Wan there. Maul saw through his former Master's plan, realising that Anakin was the apprentice Sidious sought.
Regardless, based on the season 7 of The Clone Wars, and the fact that Darth Maul was aware of Anakin Skywalker's future and his role as the Chosen One, it is very likely that Darth Maul indeed feared Darth Vader to some extent, and preferred to avoid a direct confrontation with him, at least, on his own.
Very few people knew that Darth Vader and Anakin Skywalker were the same person up to his death in 5 ABY. Imperials who knew in the current canon: Sidious (emperor), Grand Moff Tarkin, all or most of the Inquisitors, Grand Admiral Thrawn, various clones in the early empire.
Did Yularen know Vader was Anakin? Of course he did, he was the head of the Imperial Security Bureau! He knew Anakin personally during the war, so he could recognize him easily. And it was his job to know who he was really dealing with so he could be alert for any signs of possible disloyalty from any angle.
Thrawn learned that Anakin Skywalker and Darth Vader were the same person during a mission with Vader, but kept the secret to himself. Thrawn's knowledge of Anakin's history explains his surprised reaction to hearing his name in Ahsoka episode 7 and likely gives him an advantage against Ahsoka Tano.
R2-D2 was present when Padmé gave birth to Leia and Luke, so he knew Luke was Anakin's son – but what he didn't know was that Anakin became Darth Vader. In addition to that, Anakin's fall was surely a painful event in R2-D2's life, one that he definitely wouldn't like to remember or even talk about.
The duel. Darth Vader defeats Darth Maul. The two Sith Lords engaged in a lightsaber duel, going through the volcano and onto a bridge situated over a river of lava, which collapsed, though they both survived and continued their battle.
He is the primary antagonist of the original film trilogy and, as Anakin Skywalker, is the protagonist of the prequel trilogy. Born into slavery, he eventually becomes a powerful Jedi. He is lured to the dark side of the Force by Chancellor Palpatine, and transforms from Anakin into the Sith Lord Darth Vader.
Summary. Darth Vader's intense hatred extends beyond Obi-Wan Kenobi and himself to Emperor Palpatine, as revealed in Star Wars: Darth Vader #39. Vader had to tap into his deep-rooted hatred for Palpatine to overcome a deadly Scourge and destroy a Clone Wars-era droid.
The sequence calls back to a similar scene in Revenge of the Sith, when Bail Organa orders Threepio's memory be erased to prevent him from sharing information about Anakin Skywalker's fall to the dark side.
C3PO was clearly created from some sort of kit or existing prototype since every protocol droid aside from coloring looks the same. He didn't recognize him because again, they all look the same & it was decades until he saw him again. There was no reason to believe he or R2 even existed anymore.
Unfortunately, Rex and Vader never meet again though. Why didn't Palpatine feel afraid of showing his evil actions, behaviors and ways to Anakin and the Jedi anymore?
Yes, he sensed Order 66 and Anakin's turn to the dark side. In fact, it's not hard for a Jedi Master like Yoda to do so. Ahsoka Tano even felt the disturbance in the Force when she actually heard Anakin's words right when he turned to the dark side. And mind you, this was when she was on route back to…
On the contrary, Tarkin was above Vader in the Imperial hierarchy. Vader had no real ranking, but since he was the Emperor's right hand man, he could often order officers around and, occasionally, even Moffs. Tarkin was something different.
A Grand Moff received drastically increased authority, military forces, and funding as fitting their enhanced position. The position of Oversector governor was the sixth highest in the power structure after the Emperor, Supreme Commander, Grand Vizier, Advisors, and Grand Admirals.
The Sith, Darth Vader and Darth Sidious, lead the Empire, thus they outrank everyone else. In terms of the Military Rank, Vader, Tarkin and Thrawn (Possibly the other Grand Admirals and Grand Moffs as well) were all Supreme Commanders, the highest rank. Palpatine was the only one who could override their orders.
