The word "grizzlier" refers to something that is more grizzly or bear-like in appearance or demeanor. Some synonyms for this term include "fiercer," "more savage," or "more ferocious." Other options might include "more menacing," "more intimidating," or "more dangerous." Depending on the context in which it is being used, other possibilities might include "more untamed," "more unruly," or "more wild." Ultimately, the choice of synonym will depend on the exact shades of meaning that the writer is trying to convey, and the context in which the word is being used.