Grizzly bears, most of which reside in Alaska and Canada, are such gigantic dangerous beasts.

'Most adult female grizzlies weigh 130–200 kilograms (290–440 lb), while adult males weigh on average 180–360 kilograms (400–790 lb). The average total length in this subspecies is 198 centimetres (6.50 ft)'.
http://en.wikipedia.org/wiki/Grizzly_bear#Description

And grizzly bears would be named 'grisly bears', if a historical mistake didn't happen. And that name would be an excellently descriptive one. See http://en.wikipedia.org/wiki/Grizzly_bear#Name .