As we saw in his brief appearance in the finale, this is not the sweet Ben we know and love. Described as a "Machiavellian tactician, wrapped up in a pretty boy body with a rumbling inner-squid," this version of Ben is vicious, pragmatic, and hyper-vigilant. Similar to the Umbrella Academy's number two, Ben has visions of becoming the leader. Unlike Diego, Ben seems to be a bit more ruthless about ascending his rank, ready to move up at all costs.
In the graphic novels, the Sparrow Academy doesn't have an alternate Ben, and none of them have his ability. We assume that Ben retains his power to summon monsters from other dimensions and manifest them through his body. Since it seems like the Sparrow Academy benefitted from a more aware Sir Reginald, it's safe to assume that Ben has been able to grow his powers and can summon more monsters with more skill. But does a more cutthroat version of Ben mean trouble for the Umbrella Academy? Will he use their appearance to make a play for the lead spot on the Sparrows' team, or will he try to overtake the Hargreeves? They did let an alternate version of him die at a young age!