Blood, guts, and man-eaters, oh my! Feint of heart turn back now! Grisly means relating to horror or disgust, gristly means related to gristle or cartilage, and grizzly is a big ol' bear. That can eat you.
Grisly describes blood and guts, horror movie fodder, something totally repulsive. It shows up in these blood-curdling examples:
The grisly massacre — some bodies were grotesquely mutilated and defiled — shocked the country and made global headlines. (Time)
Television video showed a heavily damaged building and a grisly scene inside, with clothing and prayer mats scattered across a blood-splattered floor. (New York Times)
Gristly is gross, too, but it means related to gristle or cartilage, that yucky hard stuff in a chicken leg, for example, or the tough chewy part in any meat. Or person. Here are some gristly examples to gnaw on:
In a ham sandwich is a cold, pink punch in the face, an angry thing marbled with gristly neglect. (Guardian)
This is surrounded by a sheath of connective tissue, at first merely membranous, later becoming cartilaginous or gristly. (John Mason Tyler)
Grizzly refers to a species of brown bear found in North America. Grizzly can also refer to the color gray or gray hair: Grizzlies get their name from the white hairs that grow in their brown coats, making them look grizzled (streaked with gray).
He makes a face like a threatened grizzly bear: mouth wide open, snout muscles flexed, teeth bared. (New York Times)
All in all, if you're going out on a bear hunt, avoid grisly, gristly, and even grizzly bears. Hunt for teddy bears instead.