Espers

An Esper (エスパー, Esupā) is an individual capable of telepathy and other similar paranormal abilities.

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, and at the moment, 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
Psychokinesis: The ability to levitate and hurl matter using the mind. It can also be used to restrain opponents.

Telepathy (テレパシー, Terepashī): The ability to communicate through the mind. Possessed by Slugerous and Geryuganshoop.

Clairvoyance: The ability to see into the future. Possessed by Psykos.

Psychic Barrier: Espers can create translucent barriers around themselves. It can prevent objects from passing through including fire. It can be formed unconsciously as seen with Tatsumaki.

Chi Manipulation: An ability to immobilize and cause discomfort to a person by bending his/her life force. Pushed far enough and it can kill enemies. This power is less effective against people with strong willpower.

Weaknesses
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.