contrary to popular belief in shows, movies, and other forms of media, a villain does not have to die in order for justice to be served. there is a thing called a redemption arc. having your villain go through a series of trials and tribulations in righting their wrongs is much more interesting to read about (and more challenging for a writer) than the storyline being like "haha they died!! problem solved!! crisis averted!!"
a redemption arc does not mean that everyone suddenly forgives them for what they have done. the character may not even know that they did anything wrong. maybe, according to them, it was all justified. however, as their arc goes on, they begin to realize, through backlash and the consequence of their actions, that they messed up.
now the character must begin righting their wrongs. it should not be easy. obviously, since they're a villain, "Team Good" won't trust them. they will often be shunned, pushed away, etc which will be frustrating for them. maybe they'd even consider reverting back to being "evil" because everyone already thinks of them that way. but they shouldn't actually do it, or else Team Good definitely won't trust them, and now your redemption arc has fallen into the flames.
at the end of your arc, you don't have to make every single character trust the newly converted villain. remember that normal humans don't all get along. just because some of your Team Good characters now trust them (if only a little bit), not everyone will. and that's okay!
two examples of redemption arcs in the show are jaha and murphy. at first, jaha is presented as a jerk for sending a bunch of teenage prisoners down to die. however, the audience soon learns that he did so in order to preserve three more months of oxygen. season one ends with him staying behind on the ark so that the rest of his people can survive down on the ground. in season two, he is confident that the city of light will be this glorious thing that saves everyone. he takes the chip after finding out he's wrong because ALIE manipulated him into believing he was Bad and that his profound pain and regret would be washed away. after the COL is destroyed, he feels wholly responsible for what happened ("what have i done?" in 4x01) and tries to help the wounded/deceased as soon as he can, despite having a bullet wound himself. he then helped bellamy and clarke find the bunker. jaha is the head because all of his bad decisions have been made by the heart side of him, which is why he tries to convince clarke to keep the bunker closed during the conclave. ultimately, he dies trying to end the coup de grace lead by kara cooper in 5x02. (note: he pretty much died to further octavia's storyline as a leader with little/no advisors, and that's the tea on that).
you all know murphy's story. he was a villain who killed various members of the 100 in season one and also gave raven the wound that would make her disabled. his redemption arc begins with his Tragic Backstory™ about how he stole medicine, which he tells raven in the beginning of season two. he then saves bellamy and mel from falling down the cliff in 4x04 even though he could have let go of the seatbelt and killed them both, tried to reason with finn during his massacre, and even helped with the plan to rescue finn, which ultimately failed. murphy's redemption arc did not make him a full hero. as we see in season six, his intentions mostly rely on keeping himself alive. however, he is more attached to his friends and was able to establish relationships with them, despite his cockroach ways.
(hot take: charles pike could have had a glorious redemption arc in season 4, but the writers decided to kill him off, again, to further octavia's storyline)
now comes the question: who deserves a redemption arc and who doesn't? the biggest thing you have to consider is would your audience care to see them on Team Good? are they too far gone to be redeemed? one example of a character like this is cage wallace, the younger mount weather president from season two. he could not be redeemed because he wholeheartedly believed he was in the right and that drilling the grounders & sky people to death for their bone marrow was morally correct. he was written to be an absolutely ruthless villain and a redemption arc simply would not have worked in the narrative.
if you want to learn more about them, you can find tons of resources online!
a note: in the past, i, myself, rooted for jaha's death, which was wrong of me to do and i regret doing so. i have now learned from my mistakes and realized he wasn't as bad as my mind believed him to be.