We want to identify which one is the strongest correlation. To do so, recall that the correlation coefficient for linear correlation is a number between -1 and 1. The closest it is to 1 or to -1, the more strong is the linear relationship.
So, to identify the highest correlation, we calculate the absolute value of this coefficients. The would be
x abs(x)
0.660 0.660
0.410 0.410
-0.25 0.25
-0.83 0.83
Now, we look for the coefficient whose absolute value is closest to 1. In that case, that would be the coefficient -0.83.