which is the strongest fundamental force?

 The strongest fundamental force is the strong nuclear force, also called the strong interaction or the inter-nucleon force, this is the force within the nucleus of every atom.

 This force only exist within a space called the nuclear distance which is just a fraction of 100s of billions in diameter. This force is only present with the nucleus of an atom is absent outside the nucleus. This force is maintained by the exchange of gluons.

 Other fundamental forces are the electromagnetic, weak interaction and the gravitational force.  The gravitational is the weakest of all he force but have  the widest ranges, meaning it exist all over the earth surface unlike the strong interaction on exist within the nucleus of invisible atoms.

 The electromagnetic force is maintained by the exchange of positive or negative charges, it only exist with an electric or magnetic field, it is the second strongest fundamental force. The weak interaction or commonly called the weak force is the 3^rd strongest force of nature, it is carried by a fundamental particle called  W and Z bosons. This force only exist within the space just outside the nucleus of an atom, it is responsible of beta decay.

 The weakest of all the force is the gravitational force, has the widest range and is carried by a fundamental particle called the graviton.

 Therefore the strongest force is the strong nuclear force, it require a lots of energy to be formed through fusion and required a lots of energy to be broken though fission.