Maul eventually becomes one of the more complex antagonists of Star Wars, initially beginning as a silent Sith assassin, before eventually becoming a wildcard beholden to neither the Jedi nor the Sith, merely out for himself, his own power, and ultimately, his own revenge.
Despite his compelling charisma, dark backstory, and occasional sympathetic moments, Maul is nonetheless one of the cruelest antagonists as well, personally butchering hundreds of people in his time, as well as causing deep personal torment to specific heroes for a variety of reasons. Other villains in Star Wars are more powerful, or more evil, but when it comes to twisting the knife, Maul might take the top spot.
10 Leaving Ahsoka & Rex To Die
One of Maul's most shocking displays of power is, when aboard the ship Tribunal, he single-handedly rampages through its corridors and destroys its reactors, all while unarmed and only using the Force. As a result of this, he, Ahsoka, and Captain Rex are forced to attempt to find an escape before the Star Destroyer crash-lands.
When Ahsoka and Rex identify a craft to escape in, Maul also makes his way to it. They battle over it, but ultimately Maul prevails, and leaves the two to their deaths, in spite of Ahsoka freeing him. While she explicitly only did so to let him cause chaos, rather than to help him survive, it is nonetheless callous.
9 Killing Qui-Gon Jinn In Front Of His Apprentice
The duel between Maul and the Jedi Obi-Wan Kenobi and Qui-Gon Jinn is a fierce one, with Maul holding off both of them at times, and demonstrating his skills with a lightsaber. As it progresses, Maul separates his two enemies, leaving Obi-Wan trapped behind a laser gate as Maul duels Qui-Gon.
With a brutal move, Maul clubs Qui-Gon under the chin to stun him and then runs him through while Obi-Wan can only watch. While it is a combat situation, and far from Maul's most gratuitous kill, he nonetheless clearly relishes the moment, and enjoys making Obi-Wan see it.
8 Threatening A Child Luke On Tatooine
Once Maul loses everything across Star Wars: The Clone Wars and Star Wars: Rebels, with all of his plots foiled, he instead merely turns his eyes to revenge. Lashing out in the manner of a true Darksider, he sets out on a quest to find Obi-Wan Kenobi, and finally finish their old feud.
When Maul finds Obi-Wan on Tatooine, he takes some time to taunt Obi-Wan about his fate. As he does so, however, he guesses that Obi-Wan is not on Tatooine to protect something, but to protect someone. Although he doesn't come out and say it, there is an implied threat in the revelation, and it is this that finally goads Obi-Wan into a fight.
7 Mutilating A Clone With A Blast Door
During Maul's rampage through Tribunal, a squad of clones attempts to form a defensive checkpoint in a corridor and hold him off. When it becomes clear they cannot succeed, they seal the blast doors and attempt to escape through.
Having already killed several, Maul reaches out with the Force to the slowest of the clones, and forcibly pulls his arm back. In one of the most horrifying injuries in The Clone Wars, even if the actual wound is off-screen, the blast door slowly closes on the arm, severing it. The entire time, the Clone is screaming in fear and pain, and Maul doesn't care.
6 Throwing Kanan Out Of The Airlock
As part of his plot to bring Ezra Bridger over to the dark side, Maul seeks to deal with his master, Kanan Jarrus. Having already made one attempt at killing him, Maul fakes regret to Kanan, and apologizes for attacking him.
When Kanan responds, Maul corrects himself, saying he intended to be more thorough next time. Taking advantage of Jarrus's blindness, Maul pushes him into an airlock and has it opened, sucking Jarrus out into space. Had it not been for the Master's reflexes and Force powers, he would have faced an agonizing death.
5 Lying To Ezra About His Friends' Lives
Maul seeks to use Ezra Bridger for numerous reasons in Star Wars: Rebels' third season. He hopes to turn the boy into his apprentice, but he also seeks the information in Bridger's Jedi Holocron. It is for this reason he takes the crew of the Ghost hostage, using them to threaten Kanan and Ezra into compliance.
Maul explicitly says to Ezra that, as long as he cooperates, the crew will not die. Cruel enough, but once Ezra agrees to work with Maul, he discreetly goes back on his word and orders Ezra's friends murdered. They survive, but the intent was there.
4 Making Savage Feel Unworthy
One of Maul's more sympathetic traits is his deep love for his family. While he struggles to show it, he holds a deep attachment to both his mother, Mother Talzin, and his brother, Savage Opress. However, merely having this attachment is not the same as expressing it well.
Once Maul is restored to lucidity, he informs Savage that he is the Master, and Savage the apprentice, disarming him in a short duel to prove his point. Referring to Savage primarily as "Apprentice" from then on, Maul would lead Savage to feel a disappointment in comparison. Even as Savage lays dying, he laments that he's simply not like Maul. One of Maul's later regrets is that Savage died believing that Maul wasn't proud of him.
3 Betraying & Blinding Kanan
When Ezra finds Maul on Malachor and attempts to strike an alliance, neither Ahsoka Tano nor Kanan Jarrus is happy to see him, knowing him either personally, or by reputation. Nonetheless, the presence of three Inquisitors, and the threat of Darth Vader, presents a need for them to work together.
When the way to the Sith Holocron is clear, however, Maul betrays the Jedi. His sudden attack catches them both off-guard and blinds Jarrus with a lightsaber to the eyes. Although his attack would fail, Jarrus would remain disabled from the vicious attack.
2 Massacring Innocents To Get Obi-Wan's Attention
Once Maul is found by Opress, and once he regains his lucidity thanks to Mother Talzin, one of his first priorities is revenge against Obi-Wan Kenobi for maiming him in the first place. Rather than take the fight to the Jedi Master, he instead baits Obi-Wan out into trying to attack him.
In order to do so, Maul and Opress travel to Raydonia, where Maul contacts Obi-Wan to show him holding innocent civilians hostage. He informs Obi-Wan that if he does not travel to face him, he will kill more. To punctuate his point, he decapitates several civilians in one swing, killing them for no reason other than to make a point.
1 Murdering Duchess Satine To Hurt Obi-Wan
In further efforts to get revenge on Obi-Wan, Maul strikes at the Jedi Master's loved ones. Starting an uprising against the New Mandalorian government, Maul ensures that Obi-Wan travels to Mandalore in an attempt to protect his former love, the Duchess Satine Kryze.
Once he's there, Maul foils his plans and has both of them at his mercy. After Obi-Wan makes a genuine attempt to reach out and change Maul's mind, Maul angrily rejects him and murders Satine in cold blood. He then refuses to kill Obi-Wan, preferring to let him live with the pain, all in the pursuit of revenge.