formidable

Synonyms: appalling awful dangerous daunting dire dismaying dreadful fearful fierce frightful horrific imposing impregnable intimidating menacing redoubtable shocking terrible terrific threatening

Antonyms: feeble friendly harmless nice pleasant powerless weak

Synonyms: allpowerful arduous awesome ballbuster challenging colossal dismaying effortful great hard impressive indomitable intimidating labored laborious mammoth mighty murder onerous overpowering powerful puissant rough rough go staggering strenuous tall order toilsome tough tough proposition tremendous uphill

Antonyms: easy not hard pleasant trivial