Translation guide
Expresses that even the most optimistic outcome is limited or not very good. Often used to lower expectations or express a negative evaluation.
To say that something is only a certain way even when considering the best possible scenario, implying it's not very good.
Adverb meaning 'at most' or 'at best'. Used to indicate a limit, often with a nuance of disappointment or low expectation. Common in both spoken and written Japanese.
To reinterpret a situation or statement in the most positive light, often implying that even then it's not good.
せいぜい is more neutral and can be used in formal contexts. よくて is more colloquial and often implies a subjective judgment. せいぜい can also mean 'at most' in a quantitative sense (e.g., せいぜい100人), while よくて is less common for numbers.
There will be at most 100 participants.
Do not translate 'at best' literally as 最高で or ベストで in this context; those mean 'at the highest' or 'in the best way', not the limiting sense of 'at best'.
At best, we can finish by tomorrow.
彼の成功はせいぜい一時的なものだ。
His success is, at best, temporary.
This car will last at best another two years.
Literally 'at good', used as 'at best' when followed by a limited outcome. Often used in the pattern よくて～だ. More colloquial than せいぜい.
The movie is, at best, a way to kill time.
His proposal is, at best, a stopgap measure.
Expresses that something is insignificant or 'only' something. Can be used like 'at best' when belittling an achievement. Often has a dismissive tone.
Can sound rude or dismissive. Use only in informal situations.
Don't get carried away just because you won once; it's at best a single win.
His actions are, at best, irresponsible.
Also used in this sense, often with a phrase like ～といったところだ (it's about ~).
His ability is, at best, about that level.
The plan is, at best, a temporary solution.