What is the effect of an increase in pressure on latent heat of vaporization?

The name of the property is itself a clue here : enthalpy of vaporization. By nature, enthalpy does take into account the work required to push the atmosphere.

You can see the impact of increasing the pressure on the enthalpy of vaporization on a Mollier diagram. Increasing the pressure has the overall the effect of reducing the enthalpy of vaporization, until it becomes zero at the critical point. At this stage, there is no longer a phase change associated with vaporization.

Let be simple.

Latent heat refers to the heat required to overcome molecular bonds.

Latent heat of vapourisation of water at 1 bar, $100^\circ C$ is $2257 \frac{kJ}{kg}$. Which means, that much heat is required to break inter-molecular forces and turn into gasoeus phase.

As pressure on molecules increases they require more heat to overcome the pressure force acting or to escape and thus latent heat required is more.

While for latent heat of condensation, $335\frac{kJ}{kg}$ is to be removed, so that liquid water turns into ice at 1 bar 0 degree c.

As pressure increases, pressure acting helps in binding the molecules thus even removal of lesser amount heat would also do.

Thus as presure increases at 100 degree latent heat of vapourisation also increases while as pressure increases latent heat of condensation decreases.