Of all of its arcs, perhaps the most disliked story in Dragon Ball Z was the Buu Saga. This final major storyline was seen by some as a major dip in quality, taking the worst aspects of each previous arc and dialing them all up. Part of the Buu Saga's issues involved Majin Buu himself, as the villain was definitely a step down from Cell and Frieza.
Another villain in the Buu Saga was the wizard Babidi, who actually caused the saga to happen in the first place. Despite how integral he was, Babidi was a bit pathetic in Dragon Ball Z. The alternate Babidi in Dragon Ball Super's Future Trunks Saga, however, was much more fearsome, proactive and all-around better than the original. Here's how Future Babidi was different and how this characterization could've fixed the final storyline in Akira Toriyama's classic.
Babidi in Dragon Ball Z vs. Dragon Ball Super
Babidi appeared at the beginning of the Buu Saga, setting off its events and resurrecting the monster himself. He does so with the help of the Demon King Dabura, who he uses as a pawn. Despite this seeming megalomania, he's quickly undone twice by his own hubris once Majin Buu is resurrected, and is soon forgotten afterward.
He's much more proactive in Super's Future Timeline, however, being a prominent part of the fight between Future Trunks and Future Dabura. For instance, he uses his magic to torture Future Shin, and even attacks the Future Supreme Kai. This showcases not only how he's much more powerful, but also more willing to do whatever it takes himself to accomplish his goals. Babidi doesn't come off in the sniveling, cowardly way he does in Z; instead, feeling like a true threat in his own right. It's only when Trunks goes Super Saiyan 2 that he's able to beat both Dabura and Babidi.
How a Better Babidi Would've Fixed the Buu Saga
As mentioned, Babidi in Dragon Ball Z was portrayed as a scheming, cowardly weakling, despite his central role at the beginning of the Buu Saga. This was part of the saga's criticisms, as its earliest parts quickly became forgotten and overshadowed by the later Super Buu/Kid Buu sections.
This makes Babidi, who there paled in comparison to Dabura and Buu's power, be a sort of afterthought villain. The fact that he was soon upstaged by the monster he created only showed how pathetic he was. In Super, however, his more active role in the battles and the power level that he displays not only improves him but Dabura and Buu, as well. While his disregard for the lives of others is as strong as ever, this Babidi actually has the power to back that cruelty up and doesn't come off as a mere wizened wimp pulling strings behind the scenes. His actively fighting alongside Dabura makes it much easier to believe that the Demon King would work for Babidi.
If Babiidi had been this way in the Buu Saga, he likely would have lasted longer in its story. His pitiful death at the hands of a playful Buu would have also made a bigger impact, as he would've already been shown to be quite powerful. Thus, the fact that Buu killed him so easily would've quickly proved the immense threat of a Buu without a master. Unfortunately, this newer portrayal only showcases how poorly done he was in his original incarnation, making him a missed opportunity at best and a terrible villain in the Buu Saga at worst.