While Darth Maul was one of the most fearsome Sith Lords in the Star Wars galaxy before his fall from grace, he once received a vision from the Force where he became a Jedi Knight.
Maul and Sidious return to Malachor. After killing Peiro, Maul and Sidious returned to Malachor to expand his Sith training. During his time on Malachor, Maul breathed the ashes of the long-dead Sith and had a Force vision. In his vision, Maul was a Jedi and saved a fellow Zabrak from a creature.
Darth Maul was also strong in the Force, strong enough for Darth Sidious to raise and train him as a Sith Lord. Maul was able to use Force Choke and Force aided acrobatics.
Maul was a Zabrak from the planet Dathomir. However, though he was not Mandalorian by blood, the fact that he won the Darksaber in battle made him the last wielder before Din Djarin with a legitimate claim to the throne.
Maul confirmed to be written out of Kenobi series :( Apparently Ray Park was on set for pre production but was cut out after script was rewritten. I somewhat get they want to limit fan service and nostalgia by adding to Inquisitor story arc but at least include Obi-Wans mortal enemy in his own show.
Star Wars Rebels lead creator Dave Filoni even admitted that Maul and Vader were meant to have a fight, but he felt it would take away from the battle with Ahsoka. But as things stand, Star Wars not only lacks a fight between Vader and Maul, but the two have never even spoken to each other.
Although Obi-Wan was caught off guard by a Force push from Maul, he was clearly more than a match for the Sith apprentice. In fact, Maul trying to throw Obi-Wan into Naboo's melting pit shows he himself wasn't confident in his ability to best Kenobi with a lightsaber.
Eventually, though, Darth Maul stopped using the Darksaber. The most likely reason is that the Darksaber itself started disapproving of him as a master, thus becoming heavy and unwieldy.
Sidious revealed to Maul that he did not intend to kill his former apprentice, as he still had use for Maul; it was Sidious' hope that Maul would lead the Sith to Mother Talzin, Maul's mother and the leader of the Nightsisters, so she could be eliminated as a potential threat to the eventual Sith rule of the galaxy.
In the series, Maul and Ahsoka did not meet until the Siege of Mandalore. For reasons unknown, Maul learned her name was Ahsoka Tano but he did not know anything else about her. Ahsoka, meanwhile, was aware of Anakin and Obi-Wan's past encounters, and did not hesitate to show her hatred towards Maul.
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.
As much as fans would probably want to see Luke win this matchup, it is pretty unlikely. Luke is strong with the force, something Maul struggles with. He is so focused on his hatred that his Force sensitivity evades him. But when it comes to lightsaber combat, Maul is the definite winner.
Considering his infamy, it's hard to deny that Darth Vader is the more powerful of the two, but his victory over Maul wouldn't come easily. As the Emperor's enforcer, Vader is terrifying.
Darth Maul and Qui-Gon Jinn's duel on Tatooine in Star Wars: Episode I – The Phantom Menace revealed the Sith Order's survival to the Jedi after 1,000 years of secrecy, with Jinn somehow concluding that Maul was a Sith Lord.
As the son of Mother Talzin, the Zabrak male was taken from a young age by Sidious to act as his impressionable apprentice. The boy was raised as Darth Maul, a name he carried throughout his life. In Legends, it was insinuated that he was born "Maul" before attaining the honor of the "Darth" title.
Maul most likely knew Sidious' double role as Palpatine and Sidious when he served as Palpatine's apprentice. He definitely knew about Palpatine's goal of creating a galactic empire ruled by the Sith. Maul knows that Sidious is the Emperor.
Overall, Dooku was far more equipped to become a Sith Master than Maul was. Had he managed to overthrow Palpatine, Dooku would have been able to use his position, combat abilities, and dark side Force powers to take his place on the throne Palpatine had carved.
He regretted it because he had essentially wasted 20 years training him. But since he was an enemy at the time of his death on Tatooine, Sid was glad that he did not have to keep watching his back anymore now that the loose ends were tied off.
The very first owner of the Darksaber was the man who created it, Tarre Vizsla. Very little is canonically known about Tarre Vizsla, other than the fact he lived during the Old Republic era and was, at that time, the only Mandalorian to have ever been accepted as a Jedi.
Maul wielded the Darksaber on Dathomir. After Maul returned to Dathomir to help Mother Talzin regain her physical form, Maul was confronted by Sidious and Grievous at the Nightbrothers' village. He, along with Talzin, who had possessed Dooku, fought Sidious and Grievous.
By the time of Episode 3; Anakin is in his prime, and already one of the Jedi Order's most powerful “masters” (although technically still a knight), just behind Obi-Wan, Windu, and Yoda. Maul wouldn't stand a chance.
It's already been shown in the source material… more than once… that Darth Maul is not on Darth Sidious's level. Every time he dueled Sidious as his apprentice (in Legends) he got easily defeated. In the show Star Wars: The Clone Wars, Palpatine takes on Darth Maul and Savage Opress simultaneously.
