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at the most; at best
to the utmost; as much as possible; as much as one can
精々頑張っても今日中には終わらないな。
Even if I try my best, I won't finish it today.
彼の能力なら精々三位が限界だと思う。
With his ability, I think third place is his limit at best.
精々頑張ってみるよ。
I'll do my best.