The fundamental force underlying all chemical reactions is

Electromagnetic Force

Explanation:

Every aspect of chemical reaction is the output of electromagnetic force though the forces can take on many forms because of the quantum wave nature of particles.

The electromagnetic force has the ability to attract opposite charges such as protons and electrons and it repels same charges such as electrons and protons.

This force is an important force in the chemical reaction as it it is responsible for bonding between atoms. Though other forces are unique in their own way but they don't affect chemical reaction. Force of gravity is not strong enough to affect chemical reactions; when nuclear forces are involved in a reaction, such reaction is a nuclear reactor; not chemical reaction.

One of the roles of the electromagnetic force in chemical reaction is that it holds the electrons that are in the outer orbit around the nucleus; this, in the long run creates bonds with other chemical elements to create a visible matter.