The reason for the electron to be termed a universal particle
An electron is called a universal particle because the mass of the electron and the value of its charge remain constant irrespective of the considered material.
An electron is a fundamental particle and a proton is not a fundamental particle, that's why the electron is considered a universal particle and not a proton while both of them have a constant mass and charge.
Mass of electron
Charge of electron
Hence, the electron is called a Universal particle.