The powers of the DC Comics character Superman have changed a great deal since his introduction in the 1930s. As the character developed, his abilities were enhanced in order to maintain the interest of his audience. The extent of his powers peaked during the 1970s and 80's, to the point where it became difficult to create suitable challenges for the character. As a result, his powers were significantly reduced when his story was rebooted by writer John Byrne after the Crisis on Infinite Earths series. After Byrne's departure, Superman's powers were gradually increased again, although he still remains weaker than his Pre-Crisis incarnation.
Silver/Bronze Age (Pre-Crisis) Superman
Superman's powers were enhanced and added to from the 1940s until the mid-eighties. His powers were explained as a result of two factors: the comparatively weaker gravity of Earth, and the intensity of Earth's yellow sun. As such, Superman's powers were negated if he entered an environment similar to that of Krypton, such as the bottle city of Kandor, or if he was exposed to the solar energy of a red sun. In Silver Age stories, the powers and limitations of Superman were instantly possessed by any Kryptonians exposed to Earth or Earth-like conditions. Individuals from the planet Daxam, such as Mon-El, possessed identical powers, but were invulnerable to Kryptonite and highly susceptible to lead poisoning.
Post-Crisis
When the Superman character was revised by John Byrne shortly after Crisis on Infinite Earths, it was decided to place restrictions on his abilities. This was designed to make it easier for writers to come up with suitable challenges for the hero, and to eliminate or reduce those powers that had become too sensational or unbelievable for modern audiences. Emphasis was placed on yellow sun energy as a source for the character's powers. Superman's origin story was altered so that his powers developed gradually as his body absorbed yellow sunlight, and stories such as the Final Night series depicted the character gradually losing his powers when deprived of the sun's energy. When Superman's reserves of solar energy were depleted, as in Infinite Crisis or the Death of Superman story arcs, he required an extended period of time under a yellow sun, or some type of artificial solar enhancement in order to recharge.
Power Reduction Superman's strength was reduced to the point where he could still move tremendous amounts, but the character no longer had the ability to move planets. His speed was also reduced so that he could not exceed the speed of light. While still capable of surviving a nuclear explosion, such events would severely weaken him. Superman's sight, stamina and breath powers were also similarly reduced, and the character was also shown as requiring an oxygen mask for prolonged travel in space or underwater. His mental abilities were also curtailed to the point where intelligent humans, like geniuses Lex Luthor or Batman, could possibly outsmart him. The powers of super-ventriloquism and super-hypnosis were not generally used during this period, although it was never stated whether they had been eliminated or not.
Tactile Telekinesis An attempt was made to explain Superman's ability to fly with large objects through the introduction of tactile telekinesis. Objects that Superman touched were enveloped by an invisible telekinetic field that allowed him to move them with the force of his will. The ability also explained Superman's ability to fly. This power was the only ability originally duplicated in the Superboy clone, allowing him to emulate Superman's strength, speed, and flight capabilities, but none of his sensory powers. Over time, Superboy, or Kon-El as he came to be known, would eventually develop the same set of powers as the original.
Modern Era
After Byrne's departure from the series, Superman's powers and abilities were once again increased over time. He regained the ability to travel interstellar distances and to hold his breath for the amount of time required to make such journeys. His strength, speed, and sensory abilities were again increased, although not to Pre-Crisis levels.
The comparative weakness of the Superman character to his Pre-Crisis incarnation was definitively shown during Infinite Crisis. The Superboy-Prime character, endowed with nearly the same power levels as the Silver Age Superman, was capable of defeating large numbers of DC universe heroes, including the Teen Titans and many members of the Green Lantern Corps. The Modern Era Superman and his Earth 2 counterpart were only able to defeat Superboy-Prime after plunging him through Krypton's red sun, thereby reducing his powers.
Comparative strength
While Superman is frequently assumed to be the strongest hero in the DC universe, following the Byrne reboot, his strength tends to fluctuate depending on the amount of solar energy his cells have absorbed and the writer of the particular story. He has received a temporary boost in power after surviving a plunge into the Sun, and has had his powers depleted when deprived of such energy. The limits of how much energy Superman can absorb, and by extension the maximum limits of his power, has never been stated. Additionally, because of the solar energy that empowers him, he has often been depicted as being potentially immortal, as well as having a different ageing process, as seen in the Grant Morrison written series set in the far future of the DC Universe, DC One Million. The canonicity of this series is unknown.
Characters such as Captain Marvel, Wonder Woman, and Martian Manhunter have been described variously over time as equals, at least equal (possibly superior), or, in the last case, even superior.Captain Marvel has been able to knock him out with 1-2 punches by taking him by surprise, and Superman has stated outright that the latter has the advantage in a fist-fight due to his magic-derived powers. When the Modern Era Supergirl was introduced, it was suspected that she was stronger than her cousin, but this was due to the fact that Superman had learned to restrain his strength through years of living with weaker individuals, an ability that Kara Zor-El had not yet learned.
It is important to note that while Superman is among the strongest DC heroes, there are many who match his strength, most notably Darkseid, Bizarro, Lobo, the Cyborg Superman, Eradicator, the original Mongul, General Zod and Black Adam, while Doomsday and Despero have occasionally been shown as stronger, the former being able to effortlessly stand his ground against the entire Justice League, and the latter defeating Superman, Captain Marvel, Wonder Woman, and Power Girl at the same time. Heroes and villains with magical capabilities, like the Spectre, Zatanna, and Doctor Fate, have displayed cosmic level power vastly beyond Superman's capabilities. The Flash possesses the ability to travel at the speed of light, shunting his mass towards infinity, and enabling him to perform such feats as defeating a white martian with one punch, or almost overcoming the Anti-Monitor singlehandedly. Hal Jordan, with the will-fueled power of the Green Lantern ring, has also been cited as being a match for Superman, being able to lay him down with one punch while possessed by Parallax. The Guardians of the Universe allegedly possess abilities dwarfing those of regular Green Lantern Corps members. Kyle Rayner, inhabited by the benevolent symbiote "Ion", was recently touted as the most powerful of Earth's superheroes.
One villain that is often portrayed as vastly superior to Superman in every way is the five-dimensional entity Mr. Mxyzptlk. While the limits and nature of Mxyzptlk's powers is unclear, he is often portrayed as being, for all practical purposes, 'omnipotent,' and his encounters with Superman often amount to him simply toying with the Man of Steel.