A pit bull attacks two adults and one child in Dallas; a German shepherd attacks its owners; and a Pomeranian kills a 6-week-old girl in Los Angeles. While any size dog can become aggressive, several powerful breeds seem to have developed the worst r... (more)eputations. Some have even been banned in certain areas of the United States. In a Dog Whisperer poll, more than 10,000 viewers voted for what they thought were the most aggressive breeds.