Note: This profile contains spoilers for the game Undertale. Please do not continue if you have yet to play the game and do not want to be spoiled.
Chara is the character who is named by the player upon starting the game, along with being the first of the eight humans to ever fall into the Underground from Mount Ebott after the war between humans and monsters. The wounded child was taken in by King Asgore and Queen Toriel, becoming like a sibling to their son Asriel. Chara gave the monsters of the Underground hope, as they believed the child would be the one who bridged the gap between humans and monsters, allowing both races to live in peace.
One day, Chara fell deathly ill. Their only wish was to once again see the flowers from their village, but because only a being possessing both a powerful human soul along with a monster soul could leave the Underground, the king and queen were powerless to grant this wish. Soon, the child died, and their soul was absorbed by a grief-stricken Asriel, who transformed into a being of immense power. Using this newfound power, Asriel took Chara's body and crossed the barrier, intent on giving his sibling a proper burial in their home village. Unfortunately, upon arriving in the village, humans who saw Asriel assumed he had killed the child, immediately attacking him with killing intent. While Asriel had the power to end them all in an instant, he refused to hurt anyone and instead returned to the Underground with his sibling's body, where he collapsed in the royal garden and died, a single flower sprouting up where he fell. The entire kingdom was distraught, and the sense of hope once felt across the underground was lost.
In reality, the truth behind Chara's death was far darker and more sinister than anyone could have imagined. While searching through the True Lab, Frisk discovers a series of tapes that reveal unsettling secrets about the first fallen child. The youth who had previously been painted as an angelic messiah destined to bring peace between monsters and humans was instead revealed to have a rather cruel disposition towards those on the surface. Chara's immense disdain for humanity became increasingly evident, along with the reveal that the child, with the help of a reluctant Asriel, had planned their own death. Chara willingly consumed fresh buttercups, poisoning themself so that upon their death, Asriel would absorb their soul and the two could become a single being. After returning to town, the siblings would kill steal the souls of six humans, using this power to become a god, free the monsters, and exterminate all of humanity. While control of Asriel's body was split between the two, the true ending reveals that Asriel resisted Chara's influence and will to kill the villagers long enough to return to the Underground and perish. Despite the child being his only friend, Asriel confides in Frisk that truthfully, Chara was not a good person, and he could only assume their reasons for climbing Mount Ebott in the first place were not very happy.
Despite being dead for the entirety of the main story, Chara does in fact play a large role should the player choose to embark on a genocide run. Even from early on, as opposed to merely projecting Chara onto Frisk due to their past relationship, Flowey realizes that Frisk is merely an inhuman vessel, and they, much like him, are "empty". Throughout the course of the game, Chara's influence over Frisk will grow stronger, until they have entirely overtaken Frisk's personality. Due to the reincarnated Chara's immense hatred and determination, they will grow overwhelmingly powerful, felling even the strongest of enemies in a single blow (the only exception being Undyne). Flowey expresses his joy to have his old sibling back, relishing the thought of destroying the world alongside them. However, this joy quickly turns to panic when the flower realizes that his feelings for his reincarnated sibling are far from mutual, and Chara would not hesitate to strike Flowey down should he get in their way. Should the player manage to defeat Sans, this will indeed come to pass, as Chara has no qualms about slaughtering their adopted father and brother.
Finally, Chara will appear to the player and address them directly, stating that it was the player's Determination which allowed them to manifest in the world, once more. Chara, now far from the human they once were, will explain themself to be the very embodiment of the player's will to kill those in their way just to gain things such as exp and gold; the feeling which you use to justify to yourself the happiness you acquire from murdering an enemy just to level up. In their own words, "Every time a number increases, that feeling... That's me". Chara will then state that the two of you have reached the absolute, thus it is time to purge this timeline and move onto the next. Should the player agree, Chara will congratulate you for being such a great partner. Should the player refuse, Chara will laugh, saying it's funny you ever thought you were the one in control. Regardless of the player's choice, Chara will destroy the world, leaving nothing but an empty void. Should the player wish to return to the world, Chara will only recreate the world in exchange for your soul. Should the player accept, the child recreates the universe, but is now free to possess Frisk in all subsequent timelines.
Powers and Stats
Tier: Likely 2-B
Name: Chara, The Fallen Child (Name in-game varies depending on what the player chooses to name them)
Gender: Left ambiguous while alive, now completely inapplicable
Age: Pre-teen at the time of death
Powers and Abilities: Possession, Incorporeal, Immortality (Type 8), Timeline creation and destruction, Soul Manipulation, Determination, Time Manipulation, Reality Manipulation, Acausality, Ability to SAVE and LOAD, Regeneration (Mid-Godly)
Attack Potency: Likely Multiverse level (Destroyed reality/the game itself, which contained countless timelines. While the exact number is unknown, the sheer number of resets performed by characters such as Flowey, along with the fact that a number composed of 216 'nines' is measurable at the end of the genocide route, would easily put the number in the 2-B range.)
Speed: At least Massively Hypersonic+, likely much higher while possessing Frisk (Capable of aimdodging lasers fired from Sans' Gasterblasters, as well as Vulkin's lightning. Superior to Napstablook). Omnipresent after reaching their "absolute" (Exists as an abstract entity whose influence is everywhere in all possible timelines, as well as continuing to exist everywhere in the empty void after reality has been destroyed)
Lifting Strength: Unknown
Striking Strength: Multiversal (Destroyed the game in one blow)
Durability: Likely Multiverse level (Completely unaffected by their own destruction of the game, Exists as an abstract concept that will be brought back as long as someone with enough Determination exists), likely much higher (Ability to SAVE and LOAD makes them extremely difficult to destroy even in physical form. In their true form, Chara exists as an abstract concept capable of manifesting no matter what as long as someone experiences the drive, will, and feelings they embody, thus making them nearly impossible to actually destroy or get rid of. Returned to existence after years of non-existence simply from Frisk's entrance into the Underground.)
Range: Melee range in regular combat while possessing Frisk. Multiversal in their true form.
Intelligence: Presumably incredibly high
Standard Equipment: Real Knife, The Locket
Weaknesses: Chara needed someone with strong enough determination and capacity for violence in order to manifest, and needed to possess a host to interact with the universe before they had reached a sufficiently great level of power.