According to Coulomb’s Law, the pair of particles with the highest electric force on each other is the pair with the highest product of their charges.
According to Coulomb’s Law, the electric force between two charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them.
Therefore, the pair of particles with the highest electric force on each other would be the pair with the highest product of their charges.
For example, if one particle has a charge of +4 and the other has a charge of +6, the electric force between them would be greater than if one particle has a charge of +2 and the other has a charge of +3.