I'm honestly not sure which GT villain had the most potential to be a far better character than their actual outcome:

Baby could have been played up as a lot more complex given that he was bred and raised to singlemindedly pursue a purpose that was entirely justified at the time of his conception and had the ability to recreate the identity of his species, which would have been a good thing if he'd used an unintelligent or malevolent race as the hosts.

The Shadow Dragons, meanwhile, were an excellent concept for being designed as the final villains of the whole series, but all ended up being less-than-memorable generic monsters, their leader included. If anything, Omega Shenron as his transformed state having absorbed all the others should have been replaced with the evil giant blue Shenron seen at the beginning of the saga, in which case the final battle of the series would have been against an incarnation of an iconic godlike character established since the very beginning of the franchise rather than such a generic monster.

Super 17, on the other hand, was never a good idea, and should have been replaced with a completely new android character, such as this very game has incidentally given us years later.

In any case, it's good to know that this game is still getting new content and is willing to draw from all corners of the franchise.

"which would have been a good thing if he'd used an unintelligent or malevolent race as the hosts."

Frieza: "So, the saiyans?"

Just a passing thought, in the DBS!Broly movie, Frieza states that to have a chance against the saiyans since he'd be dead if they really wanted it. I wonder if Baby could have its big break in this scenario.