unfavorable situation; disadvantageous turn of events
Describes a situation or development that is turning against one's interests. Often used in strategic, competitive, or political contexts.
The tide of battle turned unfavorable.
The negotiations began under disadvantageous circumstances.
不利 is a general term for 'disadvantage' or 'unfavorable', while 形勢不利 specifically refers to an unfavorable situation or turn of events, often in a broader strategic sense.
形勢 means 'situation' or 'state of affairs', especially in a competitive context. 形勢不利 combines it with 不利 to explicitly state the situation is unfavorable.
Compound of 形勢 (situation, state of affairs) and 不利 (disadvantage, unfavorable). The exact historical derivation is uncertain, but the meaning is transparent from its components.