Pyrrhic
Etymology
From Pyrrhus, king of Epirus, who defeated the Romans at Heraclea in 280 BC and Asculum in 279 BC but lost so many of his best troops doing so that he could not sustain the war. He is said to have remarked that one more such victory would ruin him. "Pyrrhic victory" preserves that bitter arithmetic of winning oneself into weakness.
adjective · /PIR-ik/
Won at so great a cost that the victory is scarcely worth it, or is effectively a defeat.
What it names
The hollow win — reach for it when someone technically prevails but is left so damaged by the effort that they might as well have lost.
Example
They won the lawsuit, but the legal fees and lost customers made it a pyrrhic victory.
Related idea
A hollow victory feels empty or unsatisfying; a pyrrhic one is specifically ruinous — the cost of winning leaves you worse off than before.