astonishing

surprising greatly

• “she does an amazing amount of work”
• “the dog was capable of astonishing tricks”

so surprisingly impressive as to stun or overwhelm

• “such an enormous response was astonishing”
• “an astounding achievement”
• “the amount of money required was staggering”
• “suffered a staggering defeat”
• “the figure inside the boucle dress was stupefying”