Electrons after drop voltage

The voltage between the battery terminals is a difference in potential, key word being difference. So if for example if an electron leaving one terminal was originally at 25 eV of energy and entered the other terminal at 17 eV of energy it would be a 9 volt battery, and if it left with 59 eV and entered with 50 eV it would still be a 9 volt battery. In each case the electron lost 9 eV of energy, and that energy lost is distributed among the resistors. They still have 17 or 50 or however many electron volts of energy necessary to keep them moving. In the resistors that energy might be converted into light energy, heat, motion, or other ways to dissipate or use energy. The remaining energy stays in the electrons as their kinetic energy, which is less than what it started because it lost 9 electron volts.

If the electron has crossed the last resistor, no extra energy is required, because there is no opposition (resistance) to overcome.

This can be imagined in a situation where a body is thrown in space. It can displace itself till infinity without any extra energy. Thus once electron has crossed the last hurdle, it can reach the positive terminal of battery without any energy. The portion of the circuit that the electron is passing has 0 resistance or is a superconductor. You must be knowing current doesn't require any potential difference in a superconductor to flow.