scared stiff (?.)

• aghast
• appalled
• ashen
• astounded
• awed
• awestricken
• awestruck
• blanched
• cowed
• deadly pale
• frozen
• gray with fear
• horrified
• horror-struck
• intimidated
• pale as death
• pallid
• paralyzed
• petrified
• scared to death
• stunned
• stupefied
• terrified
• terror-crazed
• terror-haunted
• terror-ridden
• terror-riven
• terror-shaken
• terror-smitten
• terror-struck
• terror-troubled
• undone
• unmanned
• unnerved
• unstrung