Misa told me what she knew from everything Gabriel has done and said. Gabriel regretted what he did a long time ago when he knew that his guild's involvement in the underworld.
He always knew that even Heroes won't be able to escape from the underworld but he didn't expect that his guild would be the center of it all. And he just thought that whoever backing him were just greedy.
They traffic people, enslave them, and kill them. Innocent people or not, they were the victims. And Gabriel ignored them all thinking that his status as being recognized as a Hero to the people is more important.
I guess he didn't like it when he was told to kill the Saintess' children and me back in Italy. Well, if what Misa said is true, that's how Gabriel really felt.
Then the giants' existence was revealed. Not the one in a dungeon in Australia with me. But it's still related to me. Karron happened.