Odyn is a controversial character -- his actions against Helya, forcibly twisting her into a former version of herself (despite his helping him make his Val'kyr in the first place by tapping into the Shadowlands) made her an enemy of life, as well as an ally of other enemies into the future, and led to him and the Valarjar being imprisoned within the Halls of Valor for thousands of years, preventing them from fulfilling their duties as the protectors of Azeroth for many ages.
He was also the only keeper who refused to condone the blessing and empowerment of the Dragon Aspects -- he warned the others that they would eventually fail in their duties, and that only he, Odyn, was fit to defend the world they shared as Prime Designate, as the Pantheon had originally intended.
Do you agree with his choices? With his basic reasoning? Was he ultimately right or wrong? Did his choices and actions make Azeroth safer or not? Do you see him as a hero or an antagonist, or something in between?
"Like life, they shall be powerful. Like death, they shall be eternal." - Odyn