How to plot a pole in the s-plane if it has a repeated root?
Yes, the repeated real pole is at -2 or on the real axis in the s-plane. There is no imaginary component.

On a root locus plot of the closed loop poles, of a second order system, (as k is varied from 0 to infinity) the poles will converge towards each other along the real axis until they both have the same value. This is the border between underdamping and overdamping. That is to say critical damping.

Because the poles are both negative the system is stable. 

So, you would draw 2 crosses at -2 very slightly offset from each other