Toaru Majutsu no Index - Volume 22, Chapter 9: The time when a huge distortion has been corrected. Broken_Right_Hand.

Elias' world was destroyed right in front of his eyes. Only after his transmigration did he learn that there was nothing natural about its destruction.“Mother, I passed my Practical Exams! I was so lucky to get a weak world like Earth for my practicals! It only took a few months!”The person who destroyed his world was the eldest son of the family he was transmigrated to, the Ashborns.He could never forget his sister's cries when she suffered and eventually died from the virus that wreaked havoc in his world. And here he was, the person responsible, laughing.Elias wanted to repay the favor. He wanted to bring absolute ruination to these people. And for that, he had to play by their rules. He had to become the Architect of an Apocalypse…

Transmigrating into the novel, [The Emperor of Luck] Gu Xia received the despair villain system and became a small villain who is destined to be face slapped by the protagonist then eventually killed.

Having been through the plot thousands of times and being failed by the system every time, he finally snapped.

“System! What did I do wrong this time!?”

[Host, please calm down... There has been an error in the world that I have no control over. As an apology I can grant you extra rewards once you complete the plot!]

Gritting his teeth and having bloodshot red eyes Gu Xia finally had enough.

[I quit being the villain! Fuck the plot, fuck the heroine's, fuck the protagonist, fuck everyone, I just want to live my life without being face slapped! I QUIT!]

Unknowing to him all of the heroines could now hear his inner voice…

“The lifespan of a butterfly is between three days and a month, and most butterflies only live for a week.”
“Like them, I have only a few months to live, maybe less.”

–

The first time Hu Die met Jing Yu, he thought she was a world-weary girl who committed suicide.
The second time they met, he told Hu Die indifferently: “If you jump down again today, I’m not saving you again.”
Later, she told him: “Jing Yu, don’t feel sorry for me.”

Later, Jing Yu returned to the arena and won the glory that belonged to him.
Under the flashing lights, he suddenly remembered the girl’s voice, and said a nonsensical remark in front of thousands of people.

——”I’m not sad, I just think that at such a moment, it would be better if you’re here.”

“He is a whale swimming in the ocean. One day, a butterfly inadvertently broke into his frequency. That was the most beautiful moment in his life.”

- Description from Novelupdates

What got summoned was the world’s strongest sociopath.