To think you could get away with this is a grave mistake.
Tips
history
From Zeng Pu's 《孽海花》 (late Qing, chapter 25): '如今想来，真是大错特错!' - 'looking back, it really was utterly wrong!'. The doubled structure 大X特X is a productive intensifier.
grammar
The 大X特X template is a strong emphasis pattern found in other idioms: 大吵特吵 (to argue fiercely), 大书特书 (to write lavishly of). The meaning is always 'X to a very great degree'.
