In this proceeding, we report the non-perturbative potential between a heavy quark–antiquark pair in a QCD plasma at finite temperature. We compute the spin-dependent component of the thermal potential using temporal Wilson line correlators with insertions of the color-magnetic field. The calculations are performed in quenched QCD at $1.5$ times the deconfinement temperature $T_d$, on a four-dimensional lattice with spatial extent $N_s = 68$, and temporal
extents $N_\tau = 16$ and $20$. For the first time, we show that $V_{\text{ss}}(r)$ develops an imaginary part at finite temperature, a feature similar to that observed in the static potential.
Finally, we discuss the physical implications of our results for understanding the dissociation of
quarkonium bound states in the quark–gluon plasma.