Commando D was the last member of the Sentinels of Justice from the Americomics-verse, and followed similar elements to other smart superheroes. Originally, lab technician Kon-Nar of the parallel world of the Altrann was used as a template for a size-shifting super-soldier to combat the equally malleable menace known as the Vardax. These reptilian desired claiming the world as their latest conquest, and after being overwhelmed by their forces, Kon-Nar and his girlfiend Dorna escaped to Earth.
It was there that Dorna perished, bequeathing her ring to young Denny Bryant, a ring that housed a minaturized chamber which actived Kon-Nar's abilities. Using the dual identity of Connor Page the unassuming civilian and in his costume alias, Commando D! Like Earth-Four's Peter Cannon, the Thunderbolt, Commando also harnessed mythical might from the mental magnificence of a secluded civiliztion. And, like John Raymond aka the Web over on Earth-MLJ, he favored the colors green and yellow while having a red head drapped over his shoulder (a lot less nagging than Rose, Web's wife, we would imagine).
As for the Friday Fiends, the serpentile Vardax? They followed their prey to Earth-AC and drew the attention of the then formed Sentinels to retrieve imprisoned teammate Scarlet Scorpion. Yet their loss is Justice's gain in the form of a giant of man, literally and metaphorically.