Espers

An Esper (エスパー, Esupā) is an individual who possesses telepathic or psychokinetic powers.

Overview
Espers are individuals of various races that naturally awaken, possess and can harness psychic powers (超能力, Chō Nōryoku, lit. Supernatural Power). Espers are quite rare, but once awakened can become quite powerful in their own right.

Geryuganshoop claims to be the strongest psychic combatant in the universe. However this has never been confirmed. So far, Tatsumaki is shown to be the most powerful Esper in the entire series.

Certain technology can enhance psychic abilities as seen with Gearsper.

It is possible to train a person to wield psychic abilities, demonstrating that psychokinesis is not an ability restricted to espers solely.

Known Psychic Powers

 * Main article: Psychokinesis

Weaknesses
Overexertion: Espers can suffer extreme negative effects on the bodies if they exert themselves like extreme fatigue, fainting or even vomitting blood. Tatsumaki is shown to vomit blood after exerted her power to squish the fusion of Psykos and Orochi and along the way distort the entire Z-City.

Brain damage or head injury: According to Psykos, espers cannot use their power temporarily if they suffer a head injury or brain damage. This is shown when Tatsumaki cannot use her power when she suffers a concussion after Psykos sneak-attacks her from behind.

High Speed Enemies: Esper power can only work if the esper can detect the enemy's movement. If the enemy is too fast, they cannot attack accurately.

Willpower: People with exceptional willpower can resist psychic attacks. This is shown when Saitama resists Tatsumaki's chi bending and her attempt to throw him into space.