I can think of three greater ones in under a second. Putting the goatse in sitenotice for example.
That would be reverted in seconds. Very little harm done.
Other forms of abuse are bad, but can generally be resolved after a bit of discussion. A wheel war gets in the way of that discussion and makes it very difficult to resolve the initial situation- that is why Jimbo had to step in.
After the wheel war was over? In case you forget by the time I acted there had already been an attempt to shut down all discussion.
Yes, shutting down all discussion is exactly the problem I said happens with wheel wars. Everyone believes they are doing the right thing and it's the other admin that is wheel warring, but arguments along those lines pretty much never hold water. If an admin tries to shut down discussion, the correct action is to elevate the issue to the next level in the dispute resolution process (AN/I, RFC, ArbCom), not to unilaterally counter the unilateral action.