worst case; worst-case scenario
Used to refer to the most unfavorable situation or outcome, often in planning or hypothetical contexts.
In the worst case, tomorrow's game might be canceled.
You should get insurance in case of the worst-case scenario.
最悪 is an adjective meaning 'worst' or 'terrible', while 最悪の場合 is a noun phrase specifically meaning 'the worst case' or 'worst-case scenario'.
Compound of 最悪 (worst) + の (possessive particle) + 場合 (case, situation).