Relays will have a minimum operating voltage for the coil. This is the minimum voltage which when applied to the coil, will be sufficient to cause operation of the relay. This value can normally be found on the datasheet for the relay in question.
Likewise, any device will have a maximum operating voltage as well. This is usually the maximum voltage that can be applied to the component without causing damage to the component. For many relays, the maximum operating voltage for the coil is as high as 150% of the nominal operating voltage -- e.g. 4.5V for a 3V relay, 9V for a 6V relay, etc. This spec too can usually be found on the relay's datasheet...
Having re-read your question, I should say more...
The switched circuit of a relay is generally independent of the operating circuit for the relay. The purpose of a relay is to use one (usually) lower power circuit to control the operation of a higher-power circuit.
You say that you want to switch a 12V/25A load with a relay, and that the relay is to be operated via a 2V control circuit. This necessitates identifying a suitably rated relay -- one with a 2V coil, and with contacts rated for at least 25A. Other considerations are the relay physical configuration -- e.g. PCB mount, solder terminal, screw terminal, plug-in, etc, and enclosure type -- vented, sealed, etc.
It's going to be a trick to find a relay of any type with a 2V coil -- 3V coils are fairly common, and 5V coils are very common. A 2V coil may put you into the realm of a custom relay rather than a stock device...
I will be soldering on a PCB. This is for a control box in my truck that controls the added on Fog/Amber front lights. Does the attached schematic represent the best way to operate this circuit?