He sentenced The Tsar, Tsarina and their children to death. He shouted for a bloody revolution. So yes he was ruthless.
Yes. Hitler was ruthless and immoral.
Someone who has no pity or mercy and is usually cocky. Thinking he or her are unstoppable and invincible.
Merciful, or Ruthful
Being as profoundly cursed as Medusa was I think that it is little wonder that she became as vicious as she finally was.