@Veylandemar nailed it.
Raphael is more powerful than most cambions true. Here are two theories:
1. He's the son of one of the Arch Dukes of hell and this could explain his power
2. Cambions have an ambiguous place in Hell's hierarchy. Devils have soul quotas they have to meet and every devil knows it's place, knows how many souls it has to deliver to its superiors etc. Cambions don't have a place in Hell's flow chart and the have no soul debt to pay. Raphael might have been been able to exploit his ambiguous position by trading souls for the riches of the house of hope.
