na-adjective
Describes something that is the most fundamental, extreme, or final form of something. Often used in abstract or philosophical contexts.
これは究極的な選択だ。
This is the ultimate choice.
彼は人生の究極
He is searching for the ultimate purpose of life.
最終的 means 'final' in a sequential or chronological sense, whereas 究極的 emphasizes being the most extreme or fundamental.
Derived from 究極 (ultimate) + 的 (suffix forming adjectival nouns). The exact historical derivation is uncertain, but the combination is a standard pattern for creating descriptive terms.