The word Debacle means a sudden and ignominious failure; a fiasco or a complete disaster.
Let's analyze the meanings of the options:
\[\begin{array}{rl} \bullet & \text{Dandy: A man unduly devoted to style, neatness, and fashion in dress and appearance.} \\ \bullet & \text{Corker: An excellent or astonishing person or thing.} \\ \bullet & \text{Catastrophe: An event causing great and often sudden damage or suffering; a disaster.} \\ \bullet & \text{Opulence: Great wealth or luxuriousness.} \\ \end{array}\]
The word closest in meaning to debacle (a disastrous failure) is Catastrophe.