Uncle Al is the classic circus impresario: "He has ringmaster written all over him, from the scarlet coat and white jodhpurs to the top hat and waxed curled moustache. He strides across the lot like the leader of a marching band, ample belly thrust forward and issuing orders in a booming voice" (4.50). From the start, Al seems terrifying and unapproachable – he could be an even bigger villain than August.
August works his magic on Al to help get Jacob in the show. But it wasn't hard: the fact that Jacob had veterinary training at Cornell provides the circus with instant cache. Never mind that Jacob technically didn't graduate. Al immediately rewrites Jacob's history in a way that, as Rosemary explains, the "things you think on and wish on start to seem real. And then you believe them, and before you know it they're a part of your history" (13.68). It makes sense that a circus ringleader would be able to play pretend so well.
Al spends money the circus doesn't have on Rosie, who initially appears not to be worth the investment. Instead of taking responsibility for an event like this, Al forces his employees to just make it work.
And the happiest we ever see Al is when the circus does well and the money pours in:
Uncle Al is delirious, standing in the center of the hippodrome track with his arms and face raised, basking in the coins that rain down on him. He keeps his face raised even as coins bounce off his cheeks, nose, and forehead. I think he may actually be crying. (17.193)
In this moment, it's as though Al is bathing in money. Al thinks of money the same way Jacob thinks of love. Money moves and transforms Al in the same way that love illuminates Jacob. We're gonna side with Jacob on this one.
Al meets a pretty yucky end, murdered and rolled up in a piece of circus tenting. However, there are plenty of characters who would say he got exactly what he deserved. Al stiffed people on their paychecks all the time and was a dirty dealer. He frequently punished one set of people for another set's mistakes. Worst of all, he signed off on murders and beatings whenever it suited him just to save money. If he hadn't agreed to throw out so many circus folk like trash, he might not have died so soon himself.