Vermin is a pejorative word given to animals which are considered by users of the word to be pests or nuisances, most associated with the carrying of disease. Disease-carrying rodents and insects are the usual case but the term is also applied to larger animals, on the basis that they exist out of balance with a desired environment, consuming excessive resources. Pigeons, which have been widely introduced in urban environments, may be considered vermin, or, pejoratively, "flying rats" or "flying shit machines."
So according to the dictionary... it could be anything from as small as a tick... to as big as a shark... or ever bigger!
course he's probably talking about this guy...:
http://en.wikipedia.org/wiki/Vermin_%28comics%29
Vermin's strength was enhanced by the mutagenic process forced upon him. His agility, reflexes, and durability are roughly equivalent to the absolute peak attainable for the human body, but unlike his strength they do not reach superhuman levels. He has enhanced senses, particularly his sense of smell. Vermin has enhanced speed.
Vermin has the ability to control rats and stray dogs within a two mile radius of his person. It has not been clearly explained how he does this but some writers have implied it might be hyper-sonic communication.
Though Vermin has no formal martial arts training, he utilizes animal cunning and instincts which make him a very formidable hand-to-hand combatant. He once bested Spider-Man in a physical struggle, but was prevented from killing him by Kraven the Hunter.