forceful

Forceful means strong and confident in manner. Somebody who states a case and does not trail off at the end.

It usually praises: a forceful argument, a forceful personality, a forceful reminder. The line it walks is a fine one, though, since forceful is admired and forcible is about physical force and aggressive is a criticism. Applied to a woman the word has historically been used to mean something less flattering than it does of a man, which is worth being aware of. The adverb forcefully describes how something was said.