What sort of penance is that??? He killed and enslaved the ppl of Wano. He has to die according to Kin and the ppl of Wano
And when has death ever been Oda's resolution to the fucked up things he's had villains do in the series?
You think Neptune doesn't wish to see Hordy dead for killing Otohime?
You think Riku, Kyros Rebecca and Viola don't want to see Diamante dead for killing Scarlett?
Oda literally had the man whose wife was killed by Diamante fight in a battle on Dressrosa, and he still didn't have him kill him.
Oda literally has Neptune have the man who killed his wife locked up in a cell on Fishman Island, and still didn't have him kill him.
Arlong killed Nami's adoptive mother. Where is Arlong? Is he dead? Nami and Nojiko could have easily finished him off when Luffy defeated him, but did Oda have them do that?
So many villains have done so many fucked up things in the series, and a few worse than what Kaido has done, and Oda has never killed off a single one of them.