IDIOMS

leave for dead

(idiomatic, by extension, transitive) To disregard or bypass as unimportant.

Example: To abandon a person or other living creature that is injured or otherwise incapacitated, assuming that the death of the one abandoned will soon follow.
1835, Anne Laura Thorold, Letters from Brussels, in the summer of 1835:
  He stood in the middle of a narrow part of the road, stopped the horse, and struck Fyot with a heavy cudgel, leaving him for dead in the ditch.
1851, Personal Adventures of an Austrian Officer in the Hungarian War of 1848 and 1849:
  The Writer having received two wounds, is left for dead on the field
2001, R. Phillip Loy, Westerns and American Culture, 1930-1955:
  When Steele rides after them, they shoot him and leave him for dead in the desert.
2011 September 16, Ben Dirs, “Rugby World Cup 2011: New Zealand 83-7 Japan”[1], BBC Sport:
  However, the hosts hit back and hit back hard, first replacement hooker Andrew Hore sliding over, then Williams careering out of his own half and leaving several defenders for dead before flipping the ball to Nonu to finish off a scintillating move.