The game has the enemy strength set
on the characters level. For example, if you have a level 20 character
on a level 1 character's level, the enemy will be more than the strength
that the level 1 character can take. This makes the opposite true. If
you have a level 1 character, then hard levels are made easier to
compensate. Use this glitch to your advantage. Take a character with a
level 4 weapon, restart him or her at the options screen and use the
character to get his or her level 5 weapon. The AI will be on easy mode,
and their attacks will be almost nil. However, you can use your level 4
weapon and tear through their forces with no problem. This makes those
near impossible missions very easy.