Poseidon

Poseidon is the Greek God of the Sea and the third fighter in Ragnarok for the Gods' side.

[Spoiler] He was the most fearsome among all the gods and first of the gods to fall. Poseidon constantly looks down on many things from humans to fellow gods. Poseidon fought with all his might against Kojiro Sasaki as he continued to look down on him. However, Kojiro uses the third round as a chance to evolve his swordsmanship further. Kojiro succeeded and killed the most fearsome god of all by cutting him into pieces. [/Spoiler]

(Source: Shuumatsu no Valkyrie: Record of Ragnarok Wiki)