It has been suggested by some that this might mean Fain, but I still believe that Rand is the most obvious answer to this. Firstly, the other two mentions in this part of the prophecy refer to the other two ta'veren, so it seems likely that this one is far more likely to be Rand.

Second, Rand is the reborn LTT who was known as First Among Servants. The other ta'veren are referred in insulting ways (fallen and fool) so it makes sense that Rand too would be mocked in this prophecy. First Among Vermin not only insults Rand, but also implies that all Aes Sedai are vermin too. Very fitting.

And finally, the last part obviously refers to Rand, lifting his hand to break the final three seals and in doing so releasing the Dark One to touch the world freely through the bore. The DO is certainly a destroyer.