with cheating, alot! before the end battle Raze, at level 53 or so, use the save editor to boost all your xp points up as high as possible, you'll get around 175 iirc
I have read about this save editor and wanted to try it out so i started a new game. Right after starting i used the editor to boost everything i could and when i went up in level the first time i went from level 1 to 160.
