Kali: An evil sorceress cursed into her own dimension. Kali can appear in reflective surfaces, possess innocents, and wields devastating pyrokinetic power she is capable of sharing with others or projecting into the mortal realm through reflective portals. Kali must first lure a being into touching her reflection before she can possess them, her essence then shifting from her dimension into their bodies, granting her influence over the physical world.
Kali sought to steal the magick of good Witches by corrupting them and turning them evil, sharing her own powers with Aviva in hopes of gaining the ancient magick of the Halliwells.
Kali could only be vanquished by shattering her image in a mirrored surface, banishing her back to her own dimension.

Kelman, Mr: Head of the demonic Training Academy and a demon with the power to generate deadly metallic, bladed, spheres. These spheres were able to defy gravity, and move at great speeds, while remaining under Kelman’s mental control. As an upper level demon Kelman wielded the ability of adjusting, making him immune to the effects of particle stasis.
In the human world Kelman posed as a business manager, using his position to locate humans in desperate need and recruit them.
The Halliwell sisters, with the help of Tom Peters were able to defeat Kelman, impaling him on one of his own spheres.

Mr. Kelman    Leo removes Kelman's sphere

Kierkan: A “dark and powerful alchemist”. Kierkan was responsible for creating the life essence Tara. Though quite powerful Kierkan made the mistake of giving Tara both intelligence and his own abilities. Using them she was able to trick The Charmed Ones into vanquishing Kierkan before he was able to recapture her.

Kierkan and Tara's host    Kierkan is vanquished

Kierkan was domineering and arrogant, but seemed to live apart from the mortal world. The spell that vanquished him was:

Let flesh be flesh and bone be bone,
The alchemist shall transform none,
Cruel scientist of evil born,
With these words face the fire scorned

This spell required the power of three for it to be effective. It is assumed that it would have vanquished not only Kierkan, but any other alchemist as well.

Kit the catKit The Cat: The pet cat and familiar of the Charmed Ones. Kit originally belonged to a Witch that was killed by Jeremy. After its owner was murdered the cat found its way to the Halliwell home.
Kit possesses a special sense that allows it to detect magickal creatures, such as Warlocks. If it senses one it usually hisses at them. Kit can be recognized by its distinctive collar: a triquetra, the symbol of the Charmed Ones.

Klea: A member of The Brotherhood Of The Thorn and high level demon similar to Belthazor. Klea survived the Brotherhood’s Lexirom fiasco and in her human form appeared as a human, Asian, female.
Klea displayed a variant shimmering power that allowed to teleport as well as move out of dimensional phase, rendering her body invisible and immaterial but leaving her glowing eyes free to observe. This talent made Klea extremely effective at spying on others, and a valuable agent of the Brotherhood.

Klea watches from shimmered phase

Krell: One of the demon bounty hunters known as Zotars. He was sent after Belthazor when the Triad were murdered, and made a pact with the Charmed Ones to help him kill the demon.
He made the mistake of turning his back on Belthazor, and of threatening Phoebe Halliwell, and was vanquished by and energy ball. Before his death he possessed the power to teleport, enhanced strength, the ability to track the scent and blood of demons, and the ability to cast lightning bolts from his hands. Krell also displayed the ability to follow Belthazor’s shimmers, so it’s likely he was able to follow a demons scent even through teleportations.

Krell's lightning blast    Krell

Kurzon: Hoping to return to the underworld he was exiled from after a failed coup, Kurzon schemed to become the next Source after the previous one was thought vanquished by The Charmed Ones.
Kurzon commanded a demonic faction and was an extremely strong demon, capable of reconstitution, shimmering and casting energy balls; none of which saved him from vanquishing by The Charmed One’s power of three spell.

Hell threw you from its inner core,
But Earth won’t hold you anymore,
Since Heaven cannot be your place,
Your flesh and blood we now erase

Kyle: See: Chosen One.