Dueling Doctors: Doctor Double-X & Doctor Mid-Nite

Doctor Simon Ecks was an introvert scientist who developed a machine which separated his natural energy aura from himself. Seeking to quench his thirst for electricity, in order to sustain his life, Double X motivated Ecks into a life of crime. This led to a rivalry between Doctor with his Double and the Earth-One Dynamic Duo of Batman and Robin.

During their second battle, Batman countered Doctor X's Double by spawning one of his own, using Ecks' original machine. Creating Double Batman, this energy aura analogue for the Caped Crusader shared his consciousness with Batman himself. Like Double X, Double Batman could fly, emit bolts of lighting and had enhanced strength. After defeating Doctor X and his amoral aura, Double Batman ceased to exist.*

On Earth-Two, Doctor Mid-Nite was the masked alter ego of physician Doctor Charles McNider. Blinded by gunfire from a gangster, McNider learned that he had the superhuman ability to see in darkness. Devising infra-red googles to see in daylight as well as blackout bombs to disorient his foes. Charles became a masked manhunter, as well as a colleague of his Justice Society colleague, the Batman. 

By the time Mid-Nite met the Earth-One Batman and the Justice League while on a mission with the Justice Society, the Doctor developed a cryo-tuber which could which could control the central nervous system of others with electrical impulses, as well as freeze flesh.

A mutual foe of Batman and Mid-Nite was the sinister supervillain named Deathbolt, the costumed criminal originally Jake Simmons. Experimented upon by the Ultra-Humanite using an electro-dynamo, Simmons gained the ability to store and regulate electricity. He became the Earth-Two version of Doctor Double X.

While Charles McNider was the counterpart of Hans Von Hammer the so-called Enemy Ace from Earth-One's Germany, Doctor Mid-Nite's analogue would've been Batman's Doctor Double X duplicate of himself. In this way, Doctor Mid-Nite mirrored not only Earth-One's Batman as an active team-player of his World's Greatest Heroes (as the Earth-Two Batman was an honorary Justice Society member), but also reflected the costumed career of the rogue Owlman of Earth-Three's Crime Syndicate. 

Doctor Mid-Nite's counterpart on Earth-S was the avenging aviator James Albright, the goggled guardian known as Captain Midnight. Albright took on certain aspects of the Batman, including his use of gadgets and sidekicks.  As such,  the Captain was a substitute on certain adventures for the Caped Crusader of Earth-S known as Mister Scarlet, who had less chronicled adventures than the Batmen.

* Since the aura-duplicate of Batman self-destructed following his victory over Doctor Double X, this left a void around Batman filled by the chrono-energies emitted by a time-traveling Enemy Ace (who had been used as a pawn by the Lord of Time versus the Justice League and Justice Society), which led Batman into an aerial victory over the modern-day descendant of Von Hammer during a duel in competing planes.