Keiji Mogami is "This Century's Greatest Psychic" and former Psychic who turned into an evil spirit upon death.
Mogami was born with the ability to see ghosts and other powers people dreamed of, so he initially did the world good by giving advice and helping people with their problems. To that end, Mogami became one of the most famous psychics and was the first psychic to be on Japanese television. However, his mother suddenly became gravely ill and the treatment was very expensive so Mogami needed money. Due to this, outside of the spotlight, he would take on assignments from clients to solve their supernatural problems and would even take assignments from the underworld to lay death-inducing curses on others. Despite the morally dubious assignments he was taking, he continued taking them in order to pay for his mother's treatment. His mother eventually died, returned as an evil spirit and revealed that the reason she died was because all of Mogami's actions had gathered "demonics" around him which meant that she suffered.
Since he no longer needed money, he stopped all his business with the underworld. Pondering the how much of a waste his life had been, Mogami resolved to fix the world and travelled around consuming to cultivate his power for when he became an evil spirit. At one point, he encountered Dimple's group and annihilated them. He committed suicide 25 years prior to the start of the series and the event, which was caught on camera, became a famous live accident.
Powers and Stats
Name: Keiji Mogami, "The Century's Greatest Psychic"
Origin: Mob Psycho 100
Age: Was 25 at time of death, should be much older as an evil spirit
Classification: Evil Spirit
Speed: At least Massively Hypersonic+, likely Sub-Relativistic (Could go toe to toe with 100% Mob)
Lifting Strength: Class G
Striking Strength: Multi-City Block Class
Durability: Multi-City Block level (Many of Mob's attempts at attacking him ended up in futility)
Stamina: Very High
Range: Possibly multiple city blocks
Standard Equipment: None
Weaknesses: None Notable