$\text{Given }\left | -2X +9 \right | = 3,$
$\Rightarrow -2X +9 = 3 \text{ or } -\left (-2X +9 \right ) = 3,$
$\Rightarrow X = 3 \text{ or } X = 6,$
$\Rightarrow \left | -X \right |-X^{2} = \left | -3 \right |-3^{2} = -6 \text{ or } \left | -X \right |-X^{2} = \left | -6 \right |-6^{2} = -30,$
$\text{ Thus B is the correct option. }$