A very common trope in anime is to have the villain of the series be redeemed in one way or another. Sometimes the main antagonist gets redeemed early on in the series and ends up actually joining the main protagonist on whatever adventure they're on, while other times they get redeemed at the end to make the series wonderfully complete.
But there are a ton of anime villains who are forgiven by the main cast of characters without actually deserving it. They are just simply forgiven for all of their evil intent and maliciousness. There are a number of reasons why the character might forgive the villain, but sometimes it'll still make audiences ask why? (This article may contain spoilers.)
10 Akito Could Only Be Forgiven By The Pure & Kindhearted Tohru (Fruits Basket)
Akito Soma is the main antagonist in Fruits Basket in all of its iterations. Akito is the head of the Soma family and the zodiac curse itself. While the new anime has yet to release its third and final season of the series, fans of the manga know what Akito's fate becomes. Spoiler warning to fans who aren't aware, Akito is ultimately forgiven by Tohru and the zodiac members at the end of the series. This character is utterly vile, horrible, manipulative, abusive, and completely self-obsessed. But somehow, Tohru finds it in her to forgive Akito, which speaks volumes of the protagonist's heart and seems only fitting for a series like this.
9 Zabuza & Haku Showed That They Weren't Heartless After All (Naruto)
Zabuza and Haku are the first major villains in the Naruto series. They are the focus of the first main arc, and the first real threat Team Seven faces. Ultimately, Haku and Zabuza are forgiven. It is clear that Haku regrets his actions the entire time and is just doing as Zabuza wants as he owes him everything. But he doesn't actually have any ill will towards Naruto and Sasuke. Zabuza mostly fights against Kakashi and is also easily forgiven. It seems like these ninja were just on the wrong side and were actually pretty noble, something team seven learned, and they both were forgiven and mourned.
8 Hendrickson Atoned For His Sins After Becoming A Demon (Seven Deadly Sins)
Hendrickson is the main antagonist in season one of Seven Deadly Sins. He is a pretty vile character who wants nothing but destruction. He was possessed for a short while by the demon, Fraudrin, but even after the demon left his body, it seemed like Hendrickson just wanted more.
He, himself, became a demon in the climactic finale of his arc, but just after he was forgiven and atoned for his sins. Now in the series, Hendrickson seems to be one of the main protagonists and constantly helps the Holy Knights and the Seven Deadly Sins in battle to protect Liones.
7 Greed Is Forgiven After His Showdown Against Edward (Fullmetal Alchemist)
In all iterations of Fullmetal Alchemist, Greed is always forgiven for his evil deeds. In the original series, he and Ed have a massive showdown that ends in the Elrich brothers' success. But it isn't a rewarding victory as they forgive and feel for Greed. In the manga and Fullmetal Alchemist: Brotherhood, Greed returns after his defeat and cohabits Ling Yao's body. Though he originally is a villain, he ends up helping the brothers in their fight against the rest of the sins and Father, becoming one of their main allies.
6 Orochimaru Stopped Causing Trouble As Bigger Threats Emerged (Naruto)
Orochimaru is arguably the main antagonist of the original Naruto series. He is utterly vile and the reason for all of the drama that is to ensue. He places the curse mark on Sasuke during the Chunin Exams, which is what sets the entire main plot of the series into action. Orochimaru reappears a few times during Shippuden and continues to be an antagonist here and there. But it seems like by the time Boruto rolls around, Orochimaru is totally forgiven for his crimes by the higher-ups in the village and the main characters. The bulk of Konoha still are afraid of him and think of him as a villain, so he hides in a self-made house arrest situation.
5 Robin Was Betrayed By Crocodile & Joined The Straw Hat Crew (One Piece)
Robin is one of the main characters in One Piece and a vital member of the Straw Hat crew. But that wasn't always the case. When this hero was first introduced, Robin was actually a villain that served under Sir Crocodile. She fought against Luffy, Vivi, and the rest of the crew time and time again and was one of the main antagonists of that arc. But a little before the 150 episode mark, Robin changed sides. She was forgiven for her crimes and welcomed with open arms after she was betrayed by Crocodile and helped Luffy.
4 Hisoka Teams Up With Gon & Killua To Solve Bigger Issues (Hunter X Hunter)
Hisoka is one of the main antagonists of the series, but constantly gets forgiven by both Gon and Killua time and time again. Hisoka is as weird as villains come--he is utterly sadistic and enjoys the chaos he causes.
Gon and Killua have amazing hearts and their continued forgiveness of this character proves that over and over. Hisoka is not only often forgiven by Gon and Killua, but he also ends up working with them a few times to solve a bigger issue, framing him more as an anti-hero than a fully-fledged villain.
3 The Demons Come To Terms With Their Troubled Lives Just Before Death (Demon Slayer)
It seems like in the conclusion of every major arc, Tanjiro finds it in himself to discover what initially went wrong in the demon's life to provoke them to all this evil doing. He helps them come to terms with their lives just before death so that they can go on in peace. This happened during every major fight in the anime series and continues in the manga. One of the most notable examples is when Tanjiro, his friends, and Tengen Uzui (the Sound Hashira) fight against a pair of sibling Upper Moon Demons (rank six). The siblings, Daki and Gyutaro, end up replaying their human life, the struggles they went through, and what twisted them to become so evil. Daki and Gyutaro compare their lives to Tanjiro and Nezuko and are able to move on in peace, together. This is the trend of many of the demon fights Tanjiro faces in the series.
2 Sir Crocodile Has Assisted Luffy When Necessary (One Piece)
Crocodile is another character in One Piece that ends up being forgiven for all of his wrongdoings. He is the main antagonist during the Alabasta Arc, the same arc in which Nico Robin is the secondary villain before joining the Straw Hat Crew. Crocodile, however, was way worse than Robin. While Sir Crocodile isn't 100% forgiven, Luffy puts aside their differences and doesn't stray away from asking for Crocodile's help when the time comes for it in a later arc.
1 Sasuke Saved The Ninja World (Naruto Shippuden)
Arguably, Sasuke might just be one of the main villains of the Shippuden era. He not only opposed Naruto and Konoha village but also caused problems for everyone around his reluctancy to rejoin his friends. Sasuke is a main antagonist but also a main obstacle, as Naruto, Sakura, and Kakashi don't really want to defeat him. Rather, they want to save him. But even with all of the things he did wrong, like trying to kill his closest friends, he is forgiven by everyone in the village (even though many still doubt his allegiance to Konoha).