debacle

The team's poor planning turned the championship game into a complete debacle.

The school play turned into a debacle when the lead actor forgot every line and the curtain fell too early.

“When new census figures were substituted, the demonstration became a debacle; projected hospital admissions doubled, and officials withdrew the slides before the briefing ended.”
— from the passage When the Curve Breaks

“Yet her finest scene ends in a technical debacle when a harness jams, leaving her suspended above spectators unsure whether to applaud.”
— from the passage The Engineered Tempest

“When the House of Lords rejected the bill in October, the ministry's campaign became a debacle; reformers who had promised victory suddenly appeared powerless.”
— from the passage The Reform Standoff