1.
after all, in the end, ultimately
Used to express a resigned or realistic conclusion, often implying that something cannot exceed its fundamental nature or limitations.
Usage
Carries a negative or resigned nuance. It implies acceptance that something is limited by its nature. Often pairs with negative conclusions: 無理だ (impossible), 限界がある (there are limits), 通用しない (won't work).
Unlike 結局 (in the end), which is neutral, 所詮 always carries a tone of resignation, dismissal, or realism. It suggests "when you strip away the pretense."
Etymology
Originally a Buddhist term meaning "the final outcome" or "the ultimate conclusion."