Well troops from Amala are known to be superior to Pendorian ones.
I mean while the Empire was still one, their invasion force was completely devastating all of Pendor, and would have succeeded in its conquest if not for the snake cult. The knights of the old empire were also vastly more experianced, probably participating in numerous invasions beforehand. The knights would of then passed down all their skills to the next generation, and so on, thus leading to the superiority of the Empire knights to others. The Empire knights may not be the greatest armored cav, but they are great at anti-cavalry, displaying their superiority to let's say... Lion knights or Valkyries.
The shadow legion are the old remnants of the Baccus Empire, and because of that are superior to most pendorian troops
(remember that Pendor is a backwards feudal society of Petty kingdoms while the Baccus empire is a unified continent who are a vastly advanced civilization.)
The Immortals are the most elite of the empire knights, so therefore almost gods on the battlefield, their only weakness their lack of shields and mounts.