Undergrowth

Undergrowth is a villain who appears in "Urban Jungle." He wants to wipe aside humanity for their careless destruction of nature. He's extremely powerful and almost impossible to defeat by conventional means.

History
Undergrowth first appeared in "Urban Jungle." Angered that the people of Amity Park were destroying his children for urbanization, he attacked and used mind vines to turn everyone into his slaves. With Sam turned into his "daughter," he had her attack Danny. However, Danny managed to escape with his new ice powers. Sometime later, Danny returned, having finally mastered his ice powers thanks to Frostbite. Using it, he managed to destroy Undergrowth's new plant world by defeating Undergrowth. Undergrowth was reduced to a shrub and destroyed by Tucker's lawn mower.

He has a cameo in "Boxed Up Fury," in which the Box Ghost finds a reward for Undergrowth, claiming that he's an overgrown ficus.

Undergrowth's next and final appearance was in "Phantom Planet." He first appeared earlier, when Danny battled him in an attempt to prove his superiority to the "Masters' Blasters," only to fail and for them to capture Undergrowth. Undergrowth later appeared as one of the millions of ghosts who agree to help Danny save Earth from the Disasteroid.

Appearance
Undergrowth is depicted as a giant, vaguely humanoid being apparently composed of plant-matter in the form of vines with a face. He has red eyes, has darker green hands, and four spikes on his head.

Personality
Undergrowth favors plants over animal life. To him, they are his "children." He sees humans as fragile, temporary lives that won't last long. He prefers using humans to do his dirty work. However, he does show some respect to humans who want to help nature, such as Sam. He is also very proud of his own power, especially regeneration.

Sam Manson
Despite his hatred of humans, Undergrowth did sense that Sam was helping nature; as such he "replanted" her, and remolded her mind to think of him as a "father" and to help him look after his plant children.

Danny Phantom
Undergrowth sees Danny as a threat for his goals of world domination, as such he wants to feed him to his plant children.

Powers and Abilities
Undergrowth is easily one of the strongest ghosts ever and said to be nearly impossible to defeat. Many of his powers are derived from his control over plants.
 * Chlorokinesis: As the ghost of plants, Undergrowth can completely control all types of botanical life. He can also manipulate them and speed up their aging process, causing, for example, acorns to become fully grown trees in seconds, and a city to transform into a jungle in a few hours. These plants are shown to be directly linked to him, as when he was defeated, they die. His control is presumably on a global level.
 * Plant Creation: Undergrowth is able to create and manipulate all types of different plants, to the point where he can create new types of plants, never seen before, like giant venus flytraps and giant cactus men.
 * Sentience Infusion: Able to make plants able to sense, see and move on their own, although he can still control them, if the need arises.
 * Mind Control: Undergrowth can use mind vines to take control of humans, and also brainwash humans to join him, while retaining their personality, only becoming his minion. It may derived from his overshadowing.
 * Size Enhancement: He has shown that he is able to grow to enormous sizes in seconds. (Probably because he is a plant himself)
 * Intangibility: Standard ghost power.
 * Regeneration: He is one of a small number of ghosts that can easily regenerate lost body parts and reform after being blown or shattered into pieces.
 * Elongation: Undergrowth can stretch, bend, and twist as necessary.
 * Supernatural Strength: Undergrowth is capable of ripping solid concrete like paper, crushing trucks like tinfoil and bring down entire buildings with nothing but his might.
 * Spectral Body Manipulation: Undergrowth is able to manipulate the vines wrapped around his body, and use them as extra limbs. His vines are strong enough to easily crash trucks and cars and hold ghosts, as Danny's strength couldn't even tensed them. His vines can also control ghost energy, as Danny couldn't use his energy blasts or intangibility.
 * Spike Generation: Besides of having them on the vines that surround his body, he can throw them as projectiles, and they are strong enough to pierce concrete and brick walls.
 * Spore Generation: He is able to produce spores that put others to sleep.
 * Root Form: He is able to sink into the Earth then regrow in a different place, thus giving him a sort of teleportation.
 * Duplication: He could cause multiple versions of himself to grow, providing him with duplicates, only they all shared one mind.
 * Power Sharing: He can infuse other creatures, be it humans or ghosts, with some of his powers.

Weaknesses
His main weaknesses is extreme cold (and assumable fire). Danny's freeze powers weakened Undergrowth completely. His roots and brain are also his main weak spot. Also, when destroyed he will revert into a weed-like state that might take a long time to return to normal. When last seen at the end of "Urban Jungle," he had managed to regenerate into a small, rudimentary form despite his earlier defeat at Danny's hands, only to be reduced to mulch by Tucker's lawnmower.

Trivia

 * Undergrowth is one of the few evil ghosts that have never been seen being caught in the Fenton Thermos.
 * Undergrowth is voiced by legendary actor Mark Hamill, who is well known for roles like Luke Skywalker from Star Wars, and The Joker in most media featuring Batman (the latter of which found him a niche in the world as the voice of "powerful" villainous characters, like Firelord Ozai from Avatar: The Last Airbender, Malefor from The Legend of Spyro: Dawn of the Dragon, Darth Bane from Star Wars: The Clone Wars, etc.).
 * Undergrowth also serves as the main villain of Danny Phantom: Urban Jungle, a game based on his debut episode.