(Blank)
impair the strength of; weaken
debilitate
strong and healthy; vigorous; sturdy; sound
robust
strong point; that which one does with excellence
forte
active strength or force; energy
vigor
give vigor to; fill with life and energy; strengthen; enliven
invigorate
showing strong feeling; forceful; violent; furious
vehement
exciting fear by reason of strength, size, difficulty, etc.; hard to overcome; to be dreaded
formidable
wall-like defensive structure
bulwark
fortress; stronghold
citadel
incapable or being taken by assault; unconquerable; invincible
impregnable
holding fast or tending to hold fast; unyielding; stubborn; strong
tenacious
render incapable or unfit
incapacitate
forcible; compelling; powerful; convincing
cogent
falling to pieces; decayed; partly ruined or decayed through neglect
dilapidated
forceful; energetic; active
dynamic