How big do bears get - and how big did they use to get?
The 500-kg range seems about the upper limit for modern brown bears, with polars getting a little bigger. There are always stories of bigger ones (the best attested being a polar bear who weighed roughly a metric ton) and we have, of course, the prehistoric giants. My favorite, the short-faced bear, was longer and taller than any modern bear, although there is disagreement over whether he was heavier. Recent fossils from S. America, though, indicate he had still bigger relatives, bears that would make a huge modern Kodiak poop in his fur. This researcher has collected a lot of the accounts of outsized modern Kodiaks and polars. It's not all scientific data - skins are stretched, weights get exaggerated, and so on - but it's pretty darned eye-popping.
He leaves out Samson. Samson was a bear trapped alive by John (not James) "Grizzly" Adams and hauled to antebellum New York to be exhibited. He made a sensation. He was the biggest bear Adams had ever seen in many years of hunting grizzlies, and when put on a hay scale he weighed 1,503 lbs. (It's possible he had gained some "cage fat" by this point, but still, Adams' description of him as a "moving mountain" seems justified. I've never read what happened to his remains.