Answer
The slope is undefined.
Work Step by Step
We can use the slope formula to calculate the slope of a line, m, that goes through two points.
$m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$
$m=\frac{0-2}{4-4}=\frac{0+(-2)}{0}=-\frac{2}{0}$
Any number divided by 0 is undefined, so the slope is undefined.