Giant short-faced bear
The polar bear is currently the largest bear on Earth, standing at around 8 feet tall. That's still a few feet short of the biggest bear, which is thought to be the South-American giant short-faced bear. Also known as Arctodus, this bear is believed to have tipped the scales at 3,500 pounds and stood 11 feet tall, which is even taller than this diagram shows. Experts say this bear wandered South America from about 500,000 to 2 million years ago. Based on observations of a skeleton (click here for a photo) discovered in 1935 in Argentina, National Geographic reports that "there's nothing else that even comes close" in terms of this powerful meat-eater.