Power Girl

Power Girl is the Earth-Two counterpart of the Kryptonian Supergirl and first cousin to Kal-L, the Superman of Earth-Two. Possessing her cousin's superhuman strength and ability to fly, she took his place in the Justice Society of America after he entered into semi-retirement to focus on his personal life. Kara-L has since been recognized as an important member of the JSA.
After the events of the Crisis on Infinite Earths and the merging of Earth-Two into New Earth, Power Girl was led to believe that she was a descendant of the Atlantean sorcerer Arion. This was later revealed to be a deception, and Kara's true Earth-Two heritage was revealed to her during the "Infinite Crisis".

Power Girl's existence was not revealed to the general public until years after her arrival on Earth-Two. Her cousin Clark and his wife Lois provided her a family environment to assist her transition toward real life relationships. She came to regard her cousin and his wife as her "uncle" and "aunt" for raising her on Earth-Two despite being cousins by blood and marriage. 

Lane-Kent stated that they regarded her as their daughter. In her first recorded case, Kara assisted Justice Society members Flash and Wildcat in containing an artificially induced volcano that had erupted in Peking, China.  She then joined them and other young heroes Robin and Star-Spangled Kid to form a Super Squad, along with active members of the Justice Society, to defeat Brain Wave and Per Degaton's scheme for world domination. Later, she was granted full membership when she took over Superman's vacated spot on the team roster.

Having been raised by the Symbioship with artificial Kryptonian life experiences, Power Girl had trouble fitting into life on Earth, but with the help of reporter Andrew Vinson, she eventually adopted the secret identity of computer programmer Karen Starr. She developed her knowledge in this field from treatment under Wonder Woman's purple ray on Paradise Island. She never wore a mask or other disguise between her two identities and, at some point, her identity would be revealed to the public. During this time, Kara developed a close friendship with Helena Wayne, the daughter of the Earth-Two Batman and Catwoman. 

Kal-L himself returned to the mainstream universe after breaking down the walls of the paradise dimension in which he, Lois Lane-Kent, Alexander Luthor, Jr., and Superboy-Prime had been living since the end of Crisis on Infinite Earths. Appalled by the rapidly-deteriorating state of affairs on the contemporary Earth, their goal was to replace the post-Crisis planet with a recreated Earth-Two. Kal-L's first order of business was to track down Power Girl and explain the events of the original Crisis to her. He also reiterated her pre-Crisis history as his cousin. A touch from the ailing Lois Lane-Kent inexplicably restored Power Girl's memories of Earth-Two.

Soon after this revelation, she was confronted by Superboy-Prime, who rendered her unconscious. In her sleep, she was attached to a "tuning fork," a device controlled by Alex Luthor, who intended to use the device to bring back the multiple Earths. Alexander Luthor, Jr. and Psycho Pirate coerced Black Adam (who was also attached to the machine) into saying "SHAZAM!," and used the now-raw magical energy to power the tower. After the recreation of a duplicate Earth-Two, everyone associated with that Earth was subsequently transported to it. However, Power Girl would remain on the core Earth reality because of her proximity to the tower.

After arriving on the recreated Earth-Two, Lois Kent collapsed and died. This led to a violent confrontation between the two Supermen, at the end of which, Kal-L came to the realization that the recreated Earth-Two had not been a "perfect world" because "a perfect earth doesn't need a Superman."

Powers

Kryptonian Power Set: The following represents the potential superhuman abilities available to the average Kryptonian while operating within a yellow sun environment such as Earth even if demonstration of such abilities has not been explicitly shown in a canonical resource. Variations of these powers may apply depending upon the wielder in question.

Kryptonian Physiology

A Kryptonian's cellular structure is more dense, resilient and biologically more effective than human tissue. Kryptonians do not seem to possess superhuman strength levels despite their enhanced cellular ability without constant exposure to yellow solar energy. Without such charging, their strength is equitible to that of an average Earth human who engages in regular physical activity. As aliens, they possess several organs whose functions are not yet disclosed or understood but are believed to be part of and perhaps even the source of his biomatrix force field and reclamation aura. A Kryptonian's body also stores energy actively within their bio-cellular matrix as an energy pattern that is linked to their body's electromagnetic field. This energy powers most of a Kryptonian's electromagnetic capabilities such as flight and heat vision. It also supplements their physical strength.

 Solar Energy Absorption

Under optimal conditions, this is the main source of a Kryptonian's super powers and are contingent upon exposure to solar radiation from a yellow sun star system. 

 

Superhuman Strength

A Kryptonian develops enhanced physical strength after absorbing a sufficient amount of yellow solar radiation. While the exact magnitude of a Kryptonian's strength level is unknown, it is generally accepted that they are sufficiently strong enough to lift 100,000 tons or more. The specific range is unknown as a Kryptonian's strength, like their other powers, may fluctuate over time. A Kryptonian's strength is more an act of conscious will on energy fields than actual physical strength. It is through this act of conscious will that enables a Kryptonain to perform physical feats that are beyond merely applying applicable force (such as moving a mountain top without said rock crumbling under its own mass). At full power, a Kryptonian's normal strength levels are well into the multi-megaton range.

 

Invulnerability

A Kryptonian's body is nigh-invulnerable to extreme energy forces. In addition, their immune systems protects them from toxins and diseases. The most common explanations for their invulnerability is that they have a super-dense molecular structure and/or a supercharged bioelectric "aura" which acts as an invisible "force field" around their bodies within a few millimeters from their skin, and presumably within their bodies as well. The proximity of this field to their skin means that loose clothes, for example, may be burned off of of them, while cloth that is close to their body is protected by the "aura;" This phenomenon is sometimes cited as a Kryptonian's reason for wearing a skin-tight bodysuit. It is this understanding which allows them to be able to carry and move objects that would collapse under their own mass, overcoming gravity or inertia tearing them apart around their human-sized hands.

 

Superhuman Stamina

A Kryptonian has the ability to maintain continuous strenuous physical action for an undetermined period of time. Theoretically, Kryptonians have unlimited stamina as their enhanced nourishment is produced from the solar energy their cells process; however their base physical structures do need to process food stuffs as well as have the psychological need to eat and drink just as Earth humans do, despite the fact that their superhuman powers receives the majority of that power from a yellow sun. A Kryptonian does require sleep on occasion so they can dream. They can also hold their breath for an undetermined period of time.

 

Flight

A Kryptonian is able to manipulate graviton particles, in an unknown and apparently unconscious manner, to defy the forces of gravity. Under one Earth gravity, a Kryptonian is capable of speeds of multi Mach speeds in Earth's atmosphere. Their control of their flight is very precise and they can perform aerobatic feats such as hovering, flying backwards and even lifting great weights while flying.

 

Superhuman Speed

A Kryptonian is capable of enhanced reflex action and the ability to move at incredible speeds by sheer force of will. A Kryptonian can match most other speedsters in their ability to perform super-fast movements, reactions, and processes. They can use this power to disarm opponents without heightened reflexes, catch bullets or shrapnel or cross vast distances in seconds.

 

Super-Breath

Super-Breath is the ability to create hurricane force winds by blowing, and to chill their breath in order to freeze a target (this latter ability has also been called "freeze breath" and "arctic breath"). A Kryptonian can also breathe in large amounts of air, an ability used when dealing with and disposing things like clouds of poison gas.

 

Super-Hearing

Super-Hearing is the ability to hear any sound at any volume or pitch. With practice, a Kryptonian can develop enough control to block out ambient sounds to focus on a specific source/frequency. As such, they can identify a person by their heartbeat, or pick out a single voice in an entire city.

 

Heat Vision

The ability to fire beams of intense heat at a target by looking at it with the conscious act of activating this power. Visually, the power is typically depicted as two beams of red light firing from the eyes. These beams can be made invisible, allowing a Kryptonian to work undetected. The maximum temperature of their heat vision is said to be around that of a nuclear detonation. The area of effect can be consciously determined by the Kryptonian in question, down to the microscopic level.

 

Enhanced Vision

A Kryptonian also possess a superior sensory arrangement of microscopic, telescopic, infrared and ultraviolet visual capabilities. They are able to see the entire electromagnetic spectrum. Part of this mechanism is physical, part of it is believed to be psionic in nature.