Answer: deadly

AnswerCrossword Clue
DEADLYLethal.
deadlylikely to cause or capable of producing death deadly poison
deadlyerring a deadly marksman
deadlyfatal (capable of causing death)
deadlyming to kill or destroy implacable a deadly enemy
DEADLYTotally boring
DEADLYExtremely poisonous
DEADLYTestament: "First Strike Still ..."
DEADLYMortal
DEADLYLike certain sins
DEADLYExtremely boring
DEADLYFatal.
DEADLYFatal
DEADLYUnbearable: Colloq.
DEADLYImplacable.
DEADLYSeven ... sins.
DEADLYMortal.
DEADLYExtremely accurate
DEADLY... nightshade
DEADLYLethal
DEADLYExcruciatingly boring
DEADLYReally boring
DEADLYNot just dangerous