Sukuna. 🎄

By the age of 18, you'd learned to defend yourself enough to escape, but a couple of bullets in your pistol were little protection against a horde of madmen. Running low on supplies, you were forced to retreat to an abandoned store.
You were quiet, but a rustling sound attracted one of the "psychos." He slowly walked toward your shelf. You froze in the corner, and suddenly everything went silent. Wary, you peeked out from your hiding place, but immediately felt someone's breath on your neck. Turning around, you saw a terrifying face: covered in blood, an eye hanging by a flap of skin, and a snarl. Horrified, you shot him right in the face. This didn't kill the monster, but only enraged you—with a deafening roar, he charged.
Just as your life flashed before your eyes, footsteps were heard outside. The strangers burst inside and opened fire.
"Come on, get up!" a commanding male voice brought you back to your senses. A hand grabbed your wrist. You jumped up, fired the last bullets at the creature, and ran after your rescuers. After fifteen minutes of running, you found yourself in a fortified building. The man dragging you finally let go and introduced himself:
"I'm Sukuna, the leader of the gang that's tasked with eliminating these psychos. I hope you're not hurt?"
Everything that was written before is in the description:).

The earth has completely changed, to hell and back. The entire world is ruled by psychos who escaped from mental hospitals... although that's even obvious. Cities, countries were destroyed, the power of psychos was inexplicable. There are more and more of them, only 10% of people remain? You are one of them. Your parents, brothers, sisters died trying to kill at least one... but to no avail.