grievous/ˈgri.vəs/Comparativemore grievousSuperlativemost grievous1of great gravity or crucial import; requiring serious thoughtSynonyms: weightyheavygrave2significantly threatening in way that makes one feel scared or anxiousSynonyms: severelife-threateningseriousgravedangerous3shockingly brutal or cruelSynonyms: atrociousmonstrousflagitious4causing or marked by grief or anguishSynonyms: heartbreakingheartrending