Cell

Cell was the ultimate creation of Dr. Gero, who was designed to possess the abilities of the greatest fighters that visited or inhabited Earth; the result was a "perfect warrior"' possessing numerous favourable genetic traits and special abilities. He was one of the few Red Ribbon Androids that was completed by Dr. Gero's Super Computer

Appearance
In his imperfect form, unlike his larval form, Cell walks hunched over, his facial features have not yet fully developed, and he still retains an orifice like mouth (which obscures his sharp teeth), as revealed in "Silent Warrior", rather then traditional human like features seen in later forms.

Personality
Cell has an original personality, with various other characters' personality traits added; in Gero's computer redesigned the weak parts of the original personality, adding in the personalities of various different characters to make him the perfect weapon. Throughout the Android Ark, Cell's personality changes drastically with each transformation

Cell Saga
The version of Cell that plays a large role in Dragon Ball Z hails from an alternate future timeline where he has already evolved to his imperfect form. Unfortunately for him, neither Future Android 17 nor Future Android 18 are present, having already been taken out by his version of Future Trunks. After discovering the creation of a time machine by Capsule Corp, Cell proceeded to murder his timeline's version of Trunks and steal the time machine, travelling to the past of another timeline before regressing to his larval stage and hibernating for several years.

Awakening and returning to his imperfect form shortly after Androids 17 and 18 are activated, Cell proceeds to systematically slaughter the populations of entire cities; using his tail to dissolve humans into biomass which he consumes to grow in strength. Although the Z fighters were successful in destroying this timeline's version of Cell, he succeeded in tracking down and assimilating the twin androids, achieving his genetic perfection and becoming powerful enough to become a threat to the universe itself.

Although he could have destroyed Earth any time he pleased, Cell instead organised the Cell Games, a tournament in which he gave the Human race a chance to produce a champion capable of defeating him or he would destroy the planet, although this was clearly for his own amusement more than anything. After immediately defeating the Human martial artist Hercule Satan without any effort, Cell was challenged by the Sayian warrior: Goku/Kakarot.

After a difficult battle between the two, Goku was initially assumed victorious after destroying the entirety of Cell's upper body, only for him to regenerate the damage immediately afterwards. Aware that he was unable to defeat Cell, Goku made the controversial decision to concede the fight (much to Cell's surprise and frustration) and have his son Gohan, a Human-Saiyan hybrid, fight Cell in his place, to which he reluctantly agreed.

Although initially at a disadvantage, Gohan, after witnessing his father and friends attacked by Cell's spawn and the death of Android 16 by Cell's hands, became enraged to the point he achieved the second stage of the Super Sayian form. Although Cell intended for Gohan to achieve this power, the fight turned in the hybrid child's favour as he destroyed all of Cell's minions, critically damaged Cell (before allowing him to regenerate after deciding he had not suffered enough), and even freed Android 18 from Cell's body, regressing him to his semi-perfect form. Aware that he could not win, Cell elected to self-destruct, to destroy himself and take the Earth with him. After a final goodbye to his friends and his son, Goku used his instant transmission ability to teleport himself and Cell to King Kai's planet, resulting in his own death and that of King Kai.

As the remaining Z fighters recover from what had happened, Cell reappears, back in his perfect form, before fatally wounding Future Trunks. Cell proceeds to explain that he survived his own self-destruction due to the survival of a single cell left among his remains, regenerating his entire body and restoring his perfect form without requiring Androids 17 and 18 to be assimilated into his biomass. After injuring the Sayian prince Vegeta and disabling Gohan's arm, Cell attempts to kill Gohan with a massive ki energy blast, forcing him to use the Kamehameha technique to repel the blast and return it to Cell. Despite Cell possessing the apparent advantage, even as the Z fighters attacked him to weaken his blast, Gohan, with help from Goku supporting him from the other world, overpowered Cell and unleashed his full power on him. Overwhelmed by the Kamehameha wave, Cell disintegrated, screaming "I am perfect!" as every atom of his being was obliterated.

Although Cell had been destroyed, Future Trunks acknowledged that Cell still existed in his time. After returning to his own timeline and killing Future Androids 17 and 18, Trunks confronted Future Cell. Still in his imperfect form, Future Cell expressed surprise that not only did Trunks seem to know him and his intentions, but also that he had "a short lifeline." Enraged by the destruction of the twin androids and the loss of his chance to achieve perfection, Cell engaged Trunks in battle, only to be easily destroyed as a result of Trunks growing significantly stronger during his time in the past.