Unique Units:
Seanchan Swordsmen
Seanchan swordsmen are your basic heavy infantry. If they get into a fight they can take multiple hits and are able to dish out a good amount of damage in battle. You can rely on them in most fights, except when charged by cavalry or armor piercing units, though in a prolonged fight they will typically win.
Seanchan Pikes
A slightly cheaper unit, where the swordsmen can dish out damage they can take it. They can take damage quite well and when in their spear wall formation any charging cavalry will be destroyed. Against armor piercing infantry though they can fall in combat, as they just can't match damage output and their armor isn't as effective.
Deathwatch Guard
Wearing the famous dark green and red of the Deathwatch guard, this elite unit is able to cut through anyone without ever breaking to protect the Imperial Family. One of the best units on the Seanchan roster, they are a quite deadly unit. Only a cavalry charge can do much damage to them, and after charge the odds are in their favor.
Deathwatch Guard (Bodyguard)
Wearing the dark green and red and carrying these massive halberd/pikes, they can annihilate almost any unit in battle. In a battle of them against the heaviest cavalry around, I would bet on them to utterly wipe out the cavalry unless they were at quarter health and were charged from behind.
S'redit
One of the Seanchan exotic war beasts, this unit can both fire from long range and trample through enemies like a meat grinder in melee. They are tanky, heavy, and a great asset for breaking through formations. They are, however, a great target for ranged fire, and it seems that no one can resist taking a flaming potshot at them.