Currently, Leon was just a spiritual being who couldn't do anything, but weirdly enough, he could feel his blood boiling when he saw his sister and Sasha's corpses. It was only obvious that he would feel mad beyond reason. Showing him that wasn't only cruel. It was disgusting, despicable… something only a low-life would force him to watch.
For some reason, even before they would wipe out all the humans, the angels tried to create that massive magic circle on Earth. Using the mana of six planets wasn't enough to revive their good by the look of things. In any case, Leon and that Leon couldn't care less about their goals.
After fighting for dozens of years, the human race finally killed all the angels. That Leon and his friends finally had their revenge, but they didn't feel anything over it. Not only that, Hector changed. He was the group leader who now only had a couple of thousands, but slowly, he abandoned his position and eventually even disappeared, leaving Maya behind.