FEARSOME

awful, dire, direful, dread, dreaded, dreadful, fearful, fearsome, frightening, horrendous, horrific, terrible

(adjective) causing fear or dread or terror; “the awful war”; “an awful risk”; “dire news”; “a career or vengeance so direful that London was shocked”; “the dread presence of the headmaster”; “polio is no longer the dreaded disease it once was”; “a dreadful storm”; “a fearful howling”; “horrendous explosions shook the city”; “a terrible curse”

Source: WordNet® 3.1

Etymology

Adjective

fearsome (comparative more fearsome, superlative most fearsome)

frightening, especially in appearance.

(rare or archaic) fearful, frightened

Source: Wiktionary

Fear"some a.

1. Frightful; causing fear [Scotch] "This fearsome wind." Sir W. Scott

Source: Webster’s Unabridged Dictionary 1913 Edition