Although many villains spanning the Dragon Ball series are obsessed with power, chaos, and destruction, this was not entirely the case with Dragon Ball GT's Baby. As the (then) lone survivor of the Tuffle race, which was wiped out by the Saiyans with whom they shared Planet Vegeta, Baby's desire for vengeance against the remaining Saiyans had plenty of justification. In fact, the saga unpacked quite a bit of the lore behind the Saiyan-Tuffle war and established the enhanced parasites that would infect most of the Earth.
Although the war was still ongoing, its eventual outcome was clear -- the Tuffles' science and technology would not survive against the Saiyans' brutal killer instinct. In response, Baby created genetically enhanced organisms and infused them with the Tuffle King's DNA, spreading them across the universe with the hope of one day destroying the Saiyans in return for annihilating his fellow Tuffles. Although GT is widely panned by the Dragon Ball fandom and not considered canon, this saga still brought some creative ideas to a history that had been rarely explored up to that point.
Thanks to modifications by his creator Dr. Myuu (who, in a weird twist, was created by Baby himself), Baby could manipulate his body into liquid form to enter another person's body and control them -- leading to the horrifying image of Baby appearing like a wart on Vegeta's face before becoming Baby Vegeta. There were more uncomfortable moments later on, when Baby's Golden Oozaru form repeatedly expands and contracts thanks to Majuub powering up from directly inside the giant ape's body.
Grossness aside, is Baby justified in his quest to seek out and eliminate the last living Saiyans? On one hand, it's natural to harbor hatred and a desire for revenge against the race that destroyed the Tuffles and forced him away from his home planet. On the other, the reveal of his long-term Universal Tuffleization Plan fully exposed that his sadistic tendencies extended far beyond merely killing a few Saiyans -- Saiyans who, it should be noted, had nothing to do with a previous generation's war. The sympathy lessens as Baby gradually grows into a classic genocidal villain bent on ruling the universe and uses his parasites to infect the wholly innocent Earthlings.
It would have been interesting if the writers had given Baby a more sympathetic personality, having him aim for diplomacy before battle. This could have led to interesting moments of Vegeta and Goku having to figure out their place in their race's past mistakes. Considering how much Vegeta had changed by this point and Goku's endless desire to help others, they almost certainly would have cooperated in some way. Of course, thanks to Baby's hate-driven power and selfish desires, it became wholly justified to eliminate this modified parasitic version of the Tuffle race.
It's notable Baby does not appear with the nostalgic host of villains who escape from hell in the "Super Android 17" arc. This was most likely due to the writers having no desire to bring back someone who had just been defeated. That said, Baby would have gone to hell in his weakened original Tuffle state, meaning he could just as easily have been killed again in the afterlife. Either way you look at it, Baby in essence no longer exists in the Dragon Ball universe at that point. It's a sad ending for a character whose tale began as a victim of war seeking retribution for his race's demise.
