
Depends what kind of aggression you mean!
The dogs ive met most likely to bite a person, i really cant think of specific breeds -- but every single one of them, has been badly brought up using fear, and to a dog, they have ALL been punished for warning humans tht they feel threatened or uncomfortable.
Dogs most likely to cause trouble with other dogs??
Well, again im not wanting to name breeds here, but in general either, small dogs who are owned by those who dont really want a 'dog', more a toy/baby/etc, those who think a small dog misbehaving is funny, and see no need to train them.
and those dogs people somehow believe are born ready trained, border collies, golden retreivers.
Not that i think these dogs , or any dogs, are inherently more or less likely to bite another dog or a person, but border collies are the dog everyone thinks will train itself, goldies (and labs) are the ever friendly, you can do anything to it, fantastic family dog, and again, people dont realise this comes with trainig!