adjective

extremely unpleasant, horrifying, or terrible.

she suffered horrendous injuries

horrible,dreadful,horrifying,horrific,frightful,fearful,awful,terrible,shocking,appalling,hideous,grim,grisly,ghastly,harrowing,gruesome,heinous,vile,nightmarish,macabre,unspeakable,hair-raising,spine-chilling,loathsome,monstrous,abhorrent,detestable,hateful,execrable,abominable,atrocious,sickening,nauseating