Jethro says that "the saddest and most cruel April" of the five years of the Civil War was the last, in 1865. In that April, the end of the war had finally been announced with the terms of peace having been signed "by two tired men somewhere in Virginia at a place called Appomattox Court House". A few short weeks later, however, the beloved President Abraham Lincoln was assassinated. Jethro had long admired Lincoln for his honesty and steadfastness, and had written to him personally and received a response. He could not believe that fate had so cruelly "held out an almost unbelievable joy (the end of the war) and had then struck out in fury (with the death of the President) at those whose hands were outstretched".
I realize that your question asks what the worst year was for the Creightons, not the worst April. In looking at what happened to the family between 1861-1865, I would argue that, although all the years of the war were tremendously difficult ones, 1862 was most probably the worst for them. In that year, Matt Creighton was taken ill, Jethro was attacked on the way home from town and the family barn was burned by some who were angry that Bill Creighton had chosen to fight for the South, and Tom was killed at the Battle of Pittsburg Landing.