Nemesis: Martian Manhunter
Other Major Foes: Justice League of America
Appearances: 3 comics
Powers: Genetically enhanced Martian strength, super-speed, super-senses, nigh-invulnerability, invisibility, flight, and possibly other common Martian abilities.
The Marshal is the fascistic leader of the Soldiers of the Red Brotherhood, a militia which managed to temporarily wrest control of Mars II from its government and launch an invasion of planet Earth. The JLA struggled against the Marshal's forces, but there was unrest within his army that was exploited by J'onn J'onzz. In a televised battle, the Marshal stooped to cheating in unarmed combat against the Martian Manhunter, and was still beaten before the eyes of his men. The invasion was halted out of shame.
Win: The Dreaded General
Lose: B'enn B'urnzz (6-7); Commander Blanx (5-9)
Nemesis: Captain Marvel Junior
Other Major Foes: Captain Marvel, JSA
Appearances: 75+ comics.
Powers: Super strength, speed, senses, resilience and flight.
Fed a miracle food from birth by his scientist father, Albrecht Krieger grew to adult with extraordinary powers. Presented to Adolph Hitler as a perfect Aryan specimen, the newly dubbed Captain Nazi was smuggled to the United States to wreck havoc. During a battle with Captain Marvel and Mary Marvel, Captain Nazi killed an old man and crippled his grandson, Freddy Freeman. The lad was bestowed a portion of Shazam's magical power, and becoming a super-hero, Captain Marvel Junior routinely fought the Nazi responsible for changing his life.
The Marshal has only had one fight in a comic, and was straight up battered by the Alien Atlas within a few pages. Meanwhile, Captain Nazi has been in lots of fights, but most were with Captain Marvel Junior, the kid sidekick of Shazam. Also, Captain Nazi has been jobbed a number of times, perhaps most infamously in an instance of having a bunch of hypodermic needles jabbed into his eyes. This one is a toss-up, as I believe the Marshal has more raw power, but Captain Nazi has more spunk and had the opportunity to throw it around.