Undead Legionnaires, their sub-types and counterparts (like Hoplites) are the most common enemies in the God of War series, as well as Undead creatures in general. Undead Legionnaires are the basic type of this class of enemies, the Undead, which are the most common servants of the Gods and even some powerful creatures.
Dressed in the armor of ancient Greek warriors, they appear as demonic skeletons with bits of decaying flesh clinging to their bones. A frequently encountered enemy, they sometimes come in clusters and are quite varied. Early on, they wear little armor and wield short swords, but, as the games progress, they begin to appear wielding larger swords and wearing heavier armor and eventually end up wielding massive shields and scythes.
Chains of Olympus
God of War
In God of War, the Undead Legionnaires are first met during the Hydra's attack on Kratos' fleet. Later, they make up the majority of Ares' army of the undead, which is assaulting Athens, and are commonly seen as guardians in the Pandora's Temple. There are several sub-types of them, the stronger of which are the Hades Legionnaires, which Kratos fought in the Underworld. There is also a lot of related undead creatures, like Wraiths.
Ghost of Sparta
The Hoplites return in God of War: Ghost of Sparta. They are stronger than in Chains of Olympus.
During Kratos' godhood, some of these undead servants are sent by Hades to stop Kratos from reaching the Assassin and uncovering the plot to destroy his reputation with the Olympians. As always, they are no match for the Ghost of Sparta.
God of War II
They return in God of War II, but they only appear two times: in the Spiked Wall trap before the Garden of the Gods, and near the Phoenix Chamber, presumably protecting the Sisters of Fate. Their role of the most frequent enemy of the game, is now taken by the Fates Sentries.
God of War III
In God of War III, the Undead Legionnaire is replaced by a very similar enemy called the Olympus Sentry, which makes up the largest part of the gods' army.