Direful
Part of speech: adjective
Definition: inspiring fear; fearful, terrible portending disaster; portentous; ominous
Fearsome
Part of speech: adjective
Definition: frightening, especially in appearance.
Example sentence: Female violence is a specific brand of ferocity. It's invasive. A girlfight is all teeth and hair, spit and nails - a much more fearsome thing to watch than two dudes clobbering each other.