formidable

/fɔːɹˈmɪdəbəl/

IPA: /F AO1 R M AH0 D AH0 B AH0 L/

adjective
  1. 1

    Causing fear, dread, awe, or discouragement as a result of size, strength, or some other impressive feature; commanding respect; causing wonder or astonishment.

  2. 2

    Difficult to defeat or overcome.

    a formidable opponent

Source: https://en.wiktionary.org/wiki/formidable