Hector Hammond was a supervillain whose psionic powers made him dangerous.
A metahuman, the activation of Hammond's metagene gave him psionic powers. It also caused his head to grow enormously large and bring him into conflict with the Green Lantern Corps. Becoming comatose, Hammond was imprisoned in STAR Labs. Eventually, after regaining control, Hammond participated with Superman in the Psi War. Hammond escaped incarceration afterwards and later joined the Secret Society.
In his mutated form, Hammond possessed near genius level intelligence. He was also able to control people telepathically and displayed psionic and telekinetic powers.