unequivocal

admitting of no doubt or misunderstanding; having only one meaning or interpretation and leading to only one conclusion

Not equivocal; not doubtful; not ambiguous; evident; sincere; plain; as, unequivocal evidence; unequivocal words.

Latin 'unus' (one) + 'equivocus' (doubtful)

“There is more of you--and less of you, in spots, very likely--than you know. --The Member gave a slight but unequivocal start just here.”

— Oliver Wendell Holmes, Complete Project Gutenberg Oliver Wendell Holmes, Sr. Works

“This discovery was unequivocal evidence that the universe has changed radically over time (for example, via the Big Bang).”