at the worst time; at worst; at the worst level
Used to describe a situation or condition at its most severe or unfavorable point. Can function as a noun or adverbially.
Prepare assuming the worst-case scenario.
The traffic congestion in this area at its worst is terrible.
Compound of 最悪 (saiaku, 'worst') + 時 (ji, 'time'). The exact historical derivation is uncertain, but the word is a straightforward combination of these elements.