Formidable.
Synonyms:
dangerous, redoubted, terrible, tremendous.
That which is formidable is worthy of fear if encountered or opposed; as, a formidable array of troops, or of evidence. Formidable is a word of more dignity than dangerous, and suggests more calm and collected power than terrible; formidable is less overwhelming than tremendous. A loaded gun is dangerous; a park of artillery is formidable; a charge of cavalry is terrible; the full shock of great armies is tremendous. A dangerous man is likely to do mischief, and needs watching; a formidable man may not be dangerous if not attacked; an enraged maniac is terrible; the force of ocean waves in a storm, and the silent pressure in the ocean depths, are tremendous.
Antonyms:
contemptible, despicable, feeble, harmless, helpless, powerless, weak.
Prepositions:
Formidable by or in numbers; in strength; formidable to the enemy.