FORMIDABLE most nearly means:

Formidable means inspiring fear or respect; difficult to overcome or deal with due to impressive size, strength, or ability. A formidable opponent is one that will be very difficult to defeat. Root: Latin 'formidabilis' = causing fear. Military usage: formidable defenses, formidable firepower, formidable adversary. Positive usage: a formidable athlete has impressive capabilities. Key: formidable always suggests impressive power — whether in an opponent (difficult to overcome) or an ally (impressive capability).