While Cell was one of the greatest Dragon Ball villains of the original manga, he completely robbed fans of the sequel series–Dragon Ball Super–from seeing a villain who would have arguably been the deadliest enemy in the history of Dragon Ball: himself.
Cell made his first appearance in Dragon Ball chapter 361 by Akira Toriyama. Upon his debut, Cell is challenged by Piccolo who catches the villain feasting on the life forces of innocent people to make himself more powerful. The reason Cell is able to do this is that he is a specific type of Android that was created from the cells of organic life. Those cells were stolen from Goku and as well as practically everyone Goku ever came into contact with, which is why Cell was immensely powerful right from the start.
In Dragon Ball chapter 365 by Akira Toriyama, Cell had just escaped from the Z Fighters after the heroes of Earth ganged up against him in an effort to end his villainy before it had the chance to begin. Before he left, however, Cell told Piccolo everything about himself, including his origin, where he was from, and what his goals were. As he revealed to Piccolo, this version of Cell is from an alternate future who traveled back in time using Trunks’ time machine to absorb Androids 17 and 18 in order to unlock his perfect form. In his timeline, 17 and 18 were already defeated by Trunks, so time travel was the only chance Cell had at reaching his true potential. However, there was one more piece of information Cell gave the Z Fighters–one that completely eliminated the possibility of Cell’s return in Dragon Ball Super: that there was a version of him in this timeline as well.
Since Cell didn’t awaken until more than twenty years in the future, the version of him from this present timeline was essentially a fetus that was still being grown by Dr. Gero’s supercomputer in his secret underground lab. After Cell tells the Z Fighters who he is, they come to the conclusion that–while it won’t impact the adult Cell–they better go kill the baby version of the villain, so they don’t have to deal with him later–which is exactly what they do in this chapter. The tragedy of it all is that the main Dragon Ball timeline’s Cell would have been waking up around the same time as the start of Dragon Ball Super, and since Cell was an accumulation of cells collected from Goku and the people he both fights and befriends, Cell would have been way more powerful in DBS. Dragon Ball Super shows fighters like Goku, Vegeta, and even Frieza wielding the power of the gods, and if Cell was able to steal their DNA after they unlocked that amount of power, he would have been able to harness that power himself and be far stronger than he is in Dragon Ball Z.
While Dragon Ball Super: Super Hero introduced fans to Cell Max which is, by all counts, a version of Cell powerful enough to tangle with the Z Fighters at their current strength, Cell Max is not the original Cell. The original Cell could have been growing all this time right under everyone’s noses, quietly collecting samples of people’s DNA just as the one from the future had done in his original timeline, only this one would have been collecting cells from people who harness the power of cosmic gods. Since the power levels of the Z Fighters increased in Super, so would Cell's power level. However, since DBZ’s Cell spilled his guts about his origins and the fact that this timeline had its own Cell as well–sparking the Dragon Ball heroes to take violent action–fans were totally robbed of what could have been Dragon Ball Super’s greatest villain.