forceful has 1 distinct synonym spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is forceless.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
characterized by or full of force or strength (often but not necessarily physical)
“a forceful speaker”
forceful and definite in expression or action
“the document contained a particularly emphatic guarantee of religious liberty”
Synonyms, antonyms and the broader and narrower relations for forceful come from Princeton University’s WordNet. Full sources and licences.