Which bear is the only one that is almost exclusively a meat-eater?

Unlike other bear species, polar bears are almost exclusively meat eaters (carnivorous). They mainly eat ringed seals, but may also eat bearded seals. Polar bears hunt seals by waiting for them to come to the surface of sea ice to breathe. When the seal nears the surface, the polar bear will bite or grab the seal and pull it onto land to feed. They also eat walruses and whale carcasses. Polar bears will search out bird eggs and other food sources, but none of these are abundant enough to sustain the large body mass and dense populations of polar bears.

Source: National Wildlife Federation