The main enemy of the werewolves is the Wyrm, which turns people into monsters and sends forth evil critters who slaughter werewolves and defile their caerns. The entire purpose of the werewolves these days is in fact the destruction of the Wyrm. But does this help the game any, or does it actually detract from it?
The way I see it, the part of the point of being a werewolf is to be able to beat the living snot out of any normal human being. When all of your enemies are just as beastly as you are, you can't take advantage of this. Also, minions of the Wyrm are all funny-lookin', which serves as rather a harsh contrast to the graceful and beautiful Garou. When Garou fight the Wyrm's minions it usually looks rather strange, since the werewolves are using all sorts of nature abilities and stuff while the Wyrm's minions are just big, tought and ugly. Okay, then that's an oversimplification, but I hope you get my point.
But still the Wyrm makes a pretty cool enemy for the werewolves. The contrast which makes the fights look so mismatched is actually totally different when you look at it with the context that the contrast is the reason that they're fighting in the first place. The werewolves are natural, and therefore graceful and beautiful, while the Wyrm's minions are unnatural, which translates into their ugliness.
Is this enough? Well... in my opinion, not really. The Wyrm still doesn't feel exactly right as an enemy for the Garou, but it's an okay one. If you ever think that fighting the Wyrm is spoiling a campaign, I think you should go beat the tar out of some Leeches and remind yourself that you're in the World of Darkness. Ah, there ya go.