(せいぜい)

せいぜい
adverb
at most, at best
1. at most, at best
Indicating the upper limit of what can be expected; no more than.
精々(せいぜい)100(にん)ぐらいだろう
It's probably 100 people at most.
This is about all I can do.
With my current salary, I can eat out at most about once a month.
2. as much as possible, to the best of one's ability
Doing something with maximum effort (often with slight resignation or irony).
Do your best (as much as you can).
Can sound slightly dismissive depending on context
If you have time, enjoy yourself as much as you can.
You don't have much vacation left, so you'd better rest as much as you can while you have the chance.

精々(せいぜい) is an adverb with two main nuances: setting an upper limit ("at most") and doing one's best (sometimes with an ironic edge).

MEANING 1 - UPPER LIMIT:

Sets a ceiling, implying the actual amount is less than expected.

MEANING 2 - ENCOURAGEMENT/IRONY:

When used to mean "do your best," it often carries a slightly dismissive or ironic tone, depending on context.

WRITING:
Usually written in hiragana (せいぜい). The kanji 精々(せいぜい) is uncommon.

CONTRAST: