Could be an oni-type creature, but I'm guessing it's a Red Demon, same class as Oscar. Probably not actually tougher than an angel, but depending on the contract struck with it may be more reliable/controllable than an angel that has forsaken the Old Law (..and of course angels that are still following the Old Law wouldn't ever work in this position, and just forget about trying to do anything with the Thorns.)
Well.. Allison though she had to fight an angel but still busted the place up.
So we almost got to assume this is a step up from at least a young Angel.