The example you give is not a mild fork-in-the-road, but rather a "calamity" or "catastrophe"
"calamitous event" or "catastrophic event"
Etymology: Middle English calamytey, from Latin calamitat-, calamitas; perhaps akin >to Latin clades destruction
Date: 15th century
1 : a state of deep distress or misery caused by major misfortune or loss
2 : a disastrous event marked by great loss and lasting distress and suffering >"calamities of nature", "an economic calamity"
Main Entry: ca·tas·tro·phe
Etymology: Greek katastrophē, from katastrephein to overturn, from kata- + strephein to turn
1 : the final event of the dramatic action especially of a tragedy
2 : a momentous tragic event ranging from extreme misfortune to utter overthrow or ruin
3 a : a violent and sudden change in a feature of the earth b : a violent usually destructive natural event (as a supernova)
4 : utter failure : fiasco
— cat·a·stroph·ic \ˌka-tə-ˈsträ-fik\ adjective
— cat·a·stroph·i·cal·ly -fi-k(ə-)lē\ adverb