grievous

Etymology

From Middle English grevous, from Anglo-Norman grevous, from Old French grever, from Latin gravō (“I burden”). Developed in the 13th century. Equivalent to grief + -ous.

adj

1. Causing grief, pain, or sorrow.
   Heavy rain had so undermined the approach to the bridge at Mountnessing as to make it unsafe, and although Chelmsford and Colchester had decked themselves with flags and bunting, the train returned to London "with grievous disappointment to all." 1943 May and June, “Notes and News: Centenary of Railway to Colchester”, in Railway Magazine, page 176
2. Serious, grave, dire, or dangerous.