The activation energy for a simple chemical reaction $A \rightarrow B$ is $E_a$ in forward direction. The activation energy for reverse reaction :

For any reaction: $\Delta H = E_{a(forward)} - E_{a(backward)}$, so $E_{a(backward)} = E_a - \Delta H$.
[add image: potential energy diagram showing $E_a$ (forward), $E_a$ (backward) and $\Delta H$]
If the forward reaction is exothermic ($\Delta H \lt 0$), $E_{a(backward)} \gt E_a$.
If the forward reaction is endothermic ($\Delta H \gt 0$), $E_{a(backward)} \lt E_a$.
Activation energy is never negative.
So the activation energy for the reverse reaction can be less than or more than $E_a$.