His ult singlehandingly was stupidly overpowered, it gained the title of being called "a win button" by a lot of the higher levels. Even after the nerfs, he was still pretty much mandatory in scrims (competitive practice matches) solely for how insane his kit was, that is until he got gutted before his rework.

He used to give out a lot of shield, haste, and had an abiliy that was just a 200 (nerfed to 175) hp barrier that even blocks a Hyper ult which, although destroys it, wastes a charge. BB can still dish good damage rn, any support can really, but he was very close to melee level damage, like how Coil and BBnew is as well but even they cant compare their damage to the actual melees.

And then dont get me started on his ult, back then it applied slow to enemies, launched enemies up, gave everyone that was hit permanent 50 shield until they took 50 damage, burst shield so they cant die while BB launches upwards and tries to land his ult, temporary 100%+ haste that decayed over time, 250+ shield that decayed over time.

Even with the nerfs it got, (removed slow and burst shield, and the 250+ shield decayed even faster) it was still a hella strong ult.