Powerful, potent, puissant, forceful, forcible are comparable when they mean having or manifesting power to effect great or striking results.
Powerful is applicable to something which stands out from the rest of its kind as exceeding the others in its display of strength or force or in its manifestation of energy; the word also usually implies an effectiveness that has been proved rather than attributed.
Potent, though it implies powerfulness, is applicable chiefly to something which derives or seems to derive that character from some hidden or latent virtue or quality rather than from an observable or measurable power or force.
Puissant, a bookish word, refers typically to persons, to military or naval forces, or to bodies politic and connotes more the outward attributes of power; it commonly suggests a great and abiding strength.
The last two words of the group, though somewhat more restrained in their suggestion of power, nevertheless imply an ability to effect impressive results.
Forceful stresses the possession or manifestation of force as a quality; it therefore suggests marked vigor or energy or strength regardless of whether it is being exercised or not. The word is applicable even to something which makes no display of effort or violence, provided it impresses its undoubted force on the observer.
Forcible, on the other hand, suggests the actual exertion of power or force; it often implies the use of physical violence in attaining one’s ends.
Sometimes it is used in place of forceful to add to that term implications of aggressiveness, militancy, or decided potency.