In simple terms the Retributor is a Beam Laser with the Thermal Shock effect already applied. As a Powerplay weapon it is unable to be engineered.
It has reduced damage compared to its Fixed Class 1 Beam Laser counterpart; 50% of DPS and increased distro draw at 130%. It has 77% of the thermal load, however.
The heat it saves your ship is imparted to the target; but you must keep a steady stream of fire for this effect to be disruptive, which means keeping on-target continuously with a fixed weapon mount.
Against large ships the heat effect won’t be anything compared to their internal heat generation, is the common view. However it can be argued that this makes it easier to push them into overheating and therefore can be disruptive against enemy players in PVP. Smaller ships will evade your fire more easily, so you’ll find it hard to keep on target. All in all its difficult to justify the use of the Retributor in anything but very specific circumstances.