User blog comment:Gundam Legilis/Philosophy in RWBY/@comment-5041507-20150127174639/@comment-5041507-20150128041937

@LiveandSound

But the fact remains that the Grimm are indeed a massive threat, regardless of how weak the ones we've seen are. If Coco can instakill a Nevermore, just imagine the kinds of Grimm that must be out there that can challenge a fully trained huntsman, or even a full squad. They must make Goliaths seem like rapier wasps by comparison. That's our Green Goblin.

We know they're out there. CFVY's mission was delayed because they were having trouble dealing with all the Grimm. If the Grimm were all Beowolves and Ursi the kingdoms would expand without issue and the Grimm would be driven into extinction. Because that hasn't happened, we have to assume that there are stronger Grimm that we just haven't seen because RWBY isn't ready for it yet.