adjective
formidable
FOR-mi-duh-buhl/ˈfɔːrmɪdəbl/
Powerful, capable, or challenging enough to inspire respect or fear.
The overhanging cliff presents a formidable challenge to the climbers below.

Etymology
Built on “to fear,” formidable originally meant “causing fear.” Its force softened toward something so great in strength or size that it discourages effort, giving the modern sense of intimidating power or difficulty.
In context
the Assembly of the faithful true to plot the death of the new government was a difficult and perilous Enterprise still Agar was in a position to carry on a formidable conspiracy
More examples
- Repairing the aging bridge presents a formidable challenge.
- The team faces a formidable defense in tonight's game.
- He brings formidable research skills to the investigation.
Forms
formidable · more formidable · most formidable
formidably adverb — In an impressively powerful or challenging way
Similar words
- daunting
- Emphasizes difficulty that discourages someone from attempting a task.
- intimidating
- Emphasizes making someone feel afraid or less confident.
- imposing
- Emphasizes an impressive appearance or presence, especially physical size.