If I were to write story and must have the villain forgiven I will not let it just forgiven for free

.
Most frustrating part in many manga and anime is some villain just get off free no punishment and become ally


. It's so unsatisfying imagine if the MC went
"Were forgive you, in exchange for your tongue so you may never talk again"
"I want your both eye, see the world beyond your evil"
"Your hand take too many, never those hand take again"
It'll be so worth it


I don't know why, but is there an isekai named "I'm a European scientist but i reincarnated in a world using imperial unit so all my knowledge is useless and i had to go in a journey as a magician to fight evil and also teach other maggots to use coherent units because the demon realm is expending due to having better military enginneers" ? I'm pretty sure it could be fun to read !