F = {1\over 4 \pi\varepsilon_0}{q_1q_2\over r^2}
The graph between F and 1/r² is a straight line of slope {1\over 4 \pi\varepsilon_0}{q_1q_2}[/katex] passing through the origin in both cases.
Since, magnitude of the slope is more for attraction, therefore, attractive force is greater than repulsive force.