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"We all have our weaknesses, I guess. Except for you, of course."
Chloe Sullivan to Clark

The Kryptonian Clark Kent is vulnerable to kryptonite, hypnosis, magic, and the powers of certain metahumans and aliens.


Main article: Kryptonite

Kryptonite is a mineral from Clark's home planet Krypton. According to some comics, kryptonite was created when the core of Krypton became radioactive just before it exploded, but in Smallville, it was also placed in Asia, presumably by Clark's ancestor 500 years ago, suggesting that it might be a naturally-occurring radioactive element from Krypton.

The known variations of kryptonite affect Clark in different ways. Fortunately, for external exposure, Clark can protect himself from kryptonite using lead, and removal of the substance reverses the effects almost immediately. If kryptonite gets into his system, Clark's body forces it out via perspiration.

Clark beaten and weakened by green kryptonite beads.

  • Green kryptonite is Clark's most severe and dangerous vulnerability. Green kryptonite in any size or form renders Clark powerless and painfully incapacitated; he once remarked that broken ribs hurt less than green kryptonite exposure. When Clark is exposed to green kryptonite, his veins become dark and prominent, he sweats profusely, his vision blurs, and he clutches his stomach as if nauseated; it is shown that his blood literally appears to boil. He can barely stay on his feet and usually collapses to the ground in agony. Prolonged exposure renders him unconscious and would probably kill him. Clark can draw blood or bruise while in the presence of green kryptonite. Since the meteor shower, green kryptonite is found in abundance in Smallville, and Clark has fallen ill or passed out from ingestion, inhalation, and close proximity to green kryptonite. Clark's weakness to green kryptonite started at least as early as grade school; however, he did not figure out the connection with the meteor rocks until his teens, saying he is "allergic" to them. Clark and his parents keep a piece of green kryptonite in a lead box in case they ever had to subdue him in an emergency. It has been shown that even a simple layer of lead between Clark and the kryptonite is enough to prevent Clark feeling the effects of kryptonite bullets, while lead paint proves sufficient protection from conventional meteor rocks. While kryptonite weakens Clark's powers, he has been shown to still be able to use his abilities in its presence, although it takes more effort for him to use them. (Source episodes: Pilot, Metamorphosis, Leech, Phoenix, Extinction, Obsession, Onyx, Splinter)

Clark is uninhibited while exposed to red kryptonite.

  • Red kryptonite makes Clark lose his inhibitions and social conscience. Similar to the effects of alcohol, Clark becomes Kal, who is unpredictable and belligerent. While on red kryptonite, Clark is also sexually aggressive (though apparently not sexually active), flirtatious, and unconcerned with keeping his abilities a secret. He is disrespectful, uncaring of others' feelings, and can become violently dangerous. Clark also rarely swears unless under the influence of red kryptonite. In a way it is similar to the venom black symbiote from Spiderman where it brings out the darker side of the Kryptonian it comes in contact to (in this case, Clark).   (Source episodes: Red, Rush, Exodus, Exile, Unsafe, Crimson, Upgrade)
  • Blue kryptonite strips Clark of his powers, but not painfully so like green kryptonite; simply coming in contact with blue kryptonite appears to merely shut his powers down until he is no longer touching it or in its presence. (Source episodes: Blue, Savior, Salvation, Harvest)

Clark is split in two by black kryptonite.

  • Black kryptonite can separate or combine Clark from/with his Kryptonian personality Kal-El. Black kryptonite works on humans as well, physically splitting them into their good and evil personas. (Source episodes: Crusade, Onyx)

Silver kryptonite makes Clark paranoid.

  • Silver kryptonite makes Clark extremely paranoid and suspicious of those around him. Silver kryptonite's effects on Clark are similar to those of hallucinogenic drugs. His behavior becomes erratic, and he suffers extremely vivid visual and auditory hallucinations, such as perceiving balance sheets as bills. In addition, Clark manifests physical symptoms such as sweating, labored breathing, and puffy, dilated eyes, although his powers are unaffected. (Source episode: Splinter)
  • Gemstone kryptonite does not explicitly hurt Clark, but it does cause anyone who hears him to obey the first order he gives them, to the point where he even unintentionally turned himself into a killer when he revealed that he wished he could sometimes kill his opponents. (Source episode: Persuasion)
  • Gold kryptonite, when heated, can permanently scar Clark's body, although this has only happened to Clark Luthor while dealing with Lex on Earth-2. Sufficiently prolonged contact with it can also remove his powers and abilities forever. (Source episode: Luthor)



Although most metahumans received their powers and abilities from green kryptonite, Clark's vulnerability or immunity towards them seems to be random and arbitrary.

Kryptonite vulnerability

Sean steals Clark's body heat.

Clark can see the invisible man with his x-ray vision.

  • Clark could not approach Earl Jenkins due to the kryptonite embedded in his body. (Jitters)
  • Jeff Palmer was covered in a kryptonite cream that made him invisible; Clark's X-ray vision erratically turned on and off whenever he tried to look at Jeff with X-ray-vision. Also, throughout the episode, Clark was weakened slightly when near Jeff, but still had full use of his powers, apparently. (Shimmer)
  • Clark could not approach Wade Mahaney until his kryptonite tattoo wore off. (Kinetic)

Physical vulnerability

  • Sean Kelvin rendered Clark unconscious for several minutes with his heat absorption powers, although Clark was still strong enough not to be killed by this attack. (Cool)
  • Clark's powers were leeched by Eric Summers through a lightning strike when in physical contact with kryptonite. (Leech)
  • Wade Mahaney was able to injure Clark by sticking his kryptonite-enhanced tattooed hand in Clark's abdomen. (Kinetic)
  • Tyler Randall wasn't able to turn Clark to ash, but he did cause him pain with his touch and the skin where Tyler made contact turned black. (Reaper)
  • Justin Gaines threw Clark across the room when he used telekinesis against him. (Crush)
  • Eric Marsh was at first able to take Clark by surprise with his strength, but the latter managed to eventually best him by throwing him a great distance. (Witness)
  • Nathan Dean was able to incapacitate Clark with his screech. (Whisper)
  • Alicia Baker was able to teleport Clark. (Obsession)
  • Parasite was able to steal Clark's powers. (Injustice)
  • Dogs, or any animal, injected with green kryptonite steroid serums could possibly hurt Clark to some degree until maybe seasons six or seven. They could've probably severely injured him during seasons one and two, and injure him to some degree in seasons three, four and probably five.
  • Clark couldn't see anything with his powers in the tornado. (Vortex)

Mental vulnerability

Clark is possessed.

  • Cassandra Carver saw Clark's future and, unlike humans, Clark was able to see her visions when the two of them were in contact. (Hourglass)
  • Sarah Conroy entered Clark's dreams and kept him asleep, commenting that Clark's mind wasn't like others. (Slumber)
  • Jordan Cross saw a vision of Clark's future when he touched him. (Hereafter)
  • Dawn Stiles was able to possess Clark, but was driven out by exposure to kryptonite. (Spirit)
  • Kevin Grady attempted to erase Clark' memory for a few minutes; because Kryptonian physiology is different from humans, Clark developed almost total amnesia. (Blank)


Mikail trips Clark.

  • Clark was vulnerable to Dr. Frederick Walden's energy-blasting powers. (Calling)
  • Clark was vulnerable to Mikhail Mxyzptlk's control of his body. (Jinx)
  • Clark was incapacitated by Black Canary's sonic scream as it made his ears bleed. (Siren)
  • Clark was vulnerable to the Orb when it stripped him of his powers. (Arctic)
  • Clark was vulnerable to Maxima's mind control and overcome by desire when she used her powers on him. However, he was able to break this mind control when he saw Lois Lane. (Instinct)
  • Clark was vulnerable to the Persuader's atomic axe. (Legion)
  • Clark, despite all of his abilities was not nearly as powerful as the monster Doomsday. Rokk Krinn even mentioned that if Clark decided to engage him in combat, Doomsday would kill him. (Bride, Beast, Doomsday)
  • Due to the doubts and fears in Clark's heart, he was vulnerable to the dark force known as Darkseid. Darkseid preys on negative emotions in wavering souls and is determined to corrupt Clark and turn him into his slave and a weapon against mankind. However Clark eventually succeeded in putting his doubts and fears aside and managed to defeat Darkseid. (Season Ten)


Simone's hypnotic gem.


Clark is vulnerable to magic.

Main article: Magic
  • Clark was vulnerable to the magical abilities of Countess Margaret Isobel Thoreaux. His powers can be taken away by magic if the spell and the spell-caster are powerful enough; this was done by Isobel. (Spell) He was also vulnerable to the two weapons Isobel enchanted using a spell. (Sacred)
  • Clark was vulnerable to the magical powers of the Helmet of Nabu worn by Doctor Fate. With a simple hand gesture, he was able to teleport Clark to a different location and also saw his fate. (Absolute Justice)
  • Clark was not able to break free from the restraints that the Isis-possessed Lois used on him, The bonds were imbued with godly energies, therefore Clark was helpless until the energies were disrupted long enough for him to break loose. (Isis)

Other Vulnerabilities

Clark catches a cold-like illness in the Phantom Zone.

  • Clark was blinded by his own heat vision after it was reflected off of a piece of kryptonite that had been refined into a multi-cut stone for use as jewelry. In addition to the loss of sight, the skin around his eyes was red. He also experienced pain when Nathan Dean passed a blowtorch across his eyes, but the injury destroyed the scar tissue hindering his sight. (Whisper)
  • Clark was vulnerable to the Starblade, which he suspected was made of Kryptonian metal. He sustained a severe stab wound from the blade and lost a significant amount of blood before he was healed by Jor-El through Jonathan Kent. (Talisman)
  • Clark succumbed to the hallucinogenic dreams of an airborne toxin but, unlike everyone else exposed, he was able to recover on his own. (Scare)
  • While in the Phantom Zone, Clark had no physical invulnerability due to the fact that there was no yellow sun present to empower him, and he was thus able to be punched and scratched by the phantoms. He also returned to Earth with an illness that resembled the human common cold. He experienced fatigue, sneezing, a scratchy throat, and plugged-up ears. (Sneeze)
  • While Clark was on Krypton in the past, he had no abilities under Krypton's red sun; he was thus able to be easily overpowered and even bleed due to his human-level attributes. (Apocalypse)
  • Clark is vulnerable to the various intergalactic creatures escaped from the Phantom Zone. Repeated punches to the face from General Zod caused Clark to bleed from his mouth and he was powerless against the Kryptonian General. The deadly vines generated by Gloria were able to cut and impale him. Aldar easily overpowered and could have killed him. Also, Titan and Baern were all able to briefly overpower him, and Dr. Hudson was able to enter Clark's mind and keep him in a prolonged hallucination. Baern's radiation blasts were powerful enough to knock Clark back with force; Clark was stunned for several minutes. Due to being infused with DNA from Titan, Wes Keenan was also able to briefly overpower Clark, but did not cause Clark to bleed; Clark later remarked on Wes' blows "I haven't felt anything like that since going up against Titan." Bizarro was able to enter Clark's body, extract his DNA and overpower him. Presumably, Aldar, Dr. Hudson and Bizarro posed greater threats to Clark than the other Zoners, since the Martian Manhunter had to interfere in each case. (Source episodes: Zod, Wither, Fallout, Static, Labyrinth, Combat, Prototype, Phantom, Bizarro)
  • Mikhail Mxyzptlk and Tim Westcott caused Clark to choke, suggesting that he still needs to breathe air, though it later proved to be a psychological sympthom. (Jinx, Pariah)
  • Jor-El can remove Clark's powers at will, therefore making him vulnerable. In this depowered form, Clark can be killed in conventional ways, such as being shot. (Arrival, Mortal, Odyssey)


  • During Splinter, while Clark is attacking his parents under the influence of silver kryptonite, Chloe attempts to subdue Clark with the green kryptonite that Jonathan and Martha Kent keep for emergency situations, but Clark is able to superspeed out of the house. It is not proven if this was due to him being paranoid enough that he was able to summon the will to use it or if the kryptonite was simply part of the hallucination.

See also