7 letters · 7 points in Scrabble
adjective extremely harmful; bringing physical or financial ruin
adjective causing injury or blight; especially affecting with sudden violence or plague or ruin
originFrom Middle English ruynous, from Old French ruinos, ruineus, from Latin ruīnōsus. By surface analysis, ruin + -ous.
Etymology from Wiktionary, CC BY-SA 3.0