formidable Synonyms

frightful daunting difficult menacing tremendous dreadful tough terrific fearful fearsome strong frightening intimidating powerful unnerving redoubtable challenging mighty robust sophisticated staggering potent strenuous petrifying overwhelming stunning stupendous sizable sisyphean robustious rough rugged scary serious severe shocking puissant prominent prodigious sturdy swingeing whaler unyielding Armstrong all-powerful awe-inspiring backbreaking grueling gruelling jumbo