Well, there is another villain I have that I want to bounce off of you that has not depth, or at least more complexity surrounding him: Hailstone.
To sum up his character, it's a lot like this:
Why is Canterlot cursed to always worry about the Frozen North overtaking it without the crystal heart? What is the origin of the winter-driven Windigows? At what point was it left up to the entire Pegasi race to control weather?
This all could be explained by Hypothermia/Hailstone, who was peaceful for a time and was trusted by princesses Celestia and Luna to control the start and end of winter. However, due to internal reasons (I'll give more details in the thread) Hypo/Hail was driven mad and attempted to conquere Equestria by burying it in ice and snow. Of course, the princesses managed to destroy him, but not without leaving 2 legacies: the creation of the Windigows and a curse over the crystal empire to forever face the possible threat of being froze to death.
It's why the Pegasi were left with the responsibility of controlling winter as well as the other seasons; it's why Rainbow Dash couldn't control the winter clouds in "The Crystalling" parts 1 and 2.
So, the main motivation of Hailstone would be to mainly make Equestria his kingdom of ice and snow, not only freezing ponies but morphing them into his image.
However, I added in a possible reason he was driven mad:
Hailstone wanted an heir, or, at least a child to give some of his power to if he ever were to die, despite himself being an Alicorn (the first name Alicorn), who can live for thousands of years. So, he pulled a similar act that Zeus did with Hercules mother: it snowed on the mare of his choice, and she became pregnant with: Snowdrop. This wouldn't be terribly far fetched, given that Snowdrop's father is unknown and never really mentioned.
Anyone who remembers the Snowdrop video would that Snowdrop invented the snowflake, despite being blind. Snowdrop's accomplishment made Hailstone proud, and because Snowdrop was greatly recognized for her creation, Hailstone hopes the princesses would grant Snowdrop immortality, so that his daughter could work along side him forever. However.. When Snowdrop died, not only was Hailstone grief stricken, he felt the princesses cheated his beloved out of something she deserved. He was so enraged, he vowed revenge against them. But since his first form was destroyed, he left his legacy of revenge in the form of the Windigows and the Crystal Empire's problems in the Frozen North.
Decided to just call him Hailstone because Hyporthermia was too edgy.
Tell me your thoughts on this idea