This is the 3492nd most frequent Japanese word.
究極
Ultimate; final; extreme.
Here, '究極' emphasizes that this goal is of the highest or final level of aspiration.
彼は究極の目標を達成した。
He achieved the ultimate goal.
In this instance, '究極' qualifies 'truth' as being the most essential or absolute form of truth.
究極の真実を追求する旅に出た。
He embarked on a journey to pursue the ultimate truth.
In this sentence, '究極' is used as an adjective to describe the intensity or extremity of the choice being made.