train wreck

Short definition from Wiktionary

Noun

1. 1
   A train crash.
2. 2
   The wreckage resulting from a train crash.
3. 3
   A disaster, especially one which is large, chaotic, and readily seen by public observers.
4. 4
   Someone who is unbalanced and considered a mess, a disaster, one who is suffering personal ruin.
5. 5
   Dated form of train wreck.

Verb

1. 1
   To ruin utterly and catastrophically, to cause to end in disaster.