To solve the subtraction sentence \(-8 - x = -17\), we need to isolate \(x\).
Starting with the original equation, we can add \(x\) to both sides and also add 17 to both sides:
\[ -8 = -17 + x \]
Now add 17 to both sides:
\[ -8 + 17 = x \]
Calculating the left side:
\[ 9 = x \]
So, the integer that makes the subtraction sentence true is:
\[ \boxed{9} \]