The resolution to the chiasmus that is Maul and Anakin comes with each character’s death. When Luke shows compassion to Vader, refusing to execute him a the Emperor’s behest, Vader remembers that love he once knew for Padme. While he had turned away from it, it was a feeling could still remember, a feeling he could return to.
In fact, it was his love for Padme that produced the children that later served as that very reminder, bringing him back to the light in his final moments. As Anakin dies, Luke tells him he thinks he can still save him, and Anakin says “you already have, Luke. You were right. You were right about me... Tell your sister... you were right…”
On the flip side, we have Maul’s end. Maul never had the privilege of experiencing friendship or love that we know of, outside of his mother and brother, who are both dead , and weren’t exactly the best example of selfless compassion or mercy. He’s had everything taken from him several times and is now merely trying to find his place in the galaxy. Vader stands at the Emperor’s side as Maul thought he was meant to, his Shadow Collective was defeated at the end of the Clone Wars, and he was exiled into the galaxy. Alone. Again.
When Ezra Bridger discovers him on Malachor, he’s looking for vengeance. Initially, it's vengeance against the Sith, because they “took everything” from him, but once he discovers that Kenobi - the person that he thinks originally derailed his destiny - was still alive, he becomes obsessed with finding him. At this point, while he’s clearly holding a grudge against his old rival, this quest is more of a search for purpose than a quest for vengeance. Fighting Kenobi gives him a reason to even exist, for the first time in decades.
When he finds Kenobi, he’s shocked to see the simple life his rival has taken, and even more surprised that Obi-Wan has no desire to fight him. When he tries to goad him into a confrontation, the Jedi Master simply states: “If you define yourself by your power to take life, your desire to dominate, to possess, then you have nothing” in what is one of the only examples of Maul experiencing compassion or mercy. Unfortunately, Maul didn’t have the privilege of experiencing this kind of selflessness earlier in his life as Anakin did.
Kenobi quickly defeats him. Vader died in the arms of his son, but Maul’s last words came as he’s held by his oldest nemesis hoping the Chosen One “will avenge us.” Still clinging to his thirst for violence and need for vengeance. Even though he was shown a similar compassion in his final moments as Vader did in his, he had no context for it, and thus had no capacity for redemption or a peaceful end.
Had Maul benefitted from the blessing of being born to Shmi, loved by Padme, experienced the bond of brotherhood with Obi-Wan, and had his own child risk life and limb to redeem him, could he have shared in that same peace Vader did at the end? It could obviously go both ways, but those are the components of Vader's to the light. They could have done the same for Maul. Vader’s story is tragic, but his tragedy is in his fall, in the fact that he first had love and friendship, but he turned away. The tragedy of Maul, however, is that he never even had that chance.