Painful Past

These two have very stressing past from their memory from different dimensions. Gage's past shows how much abused  that humanity served and deaths. For Sunset's, she became a ruthless fool to destroy Equestria by hypnotize every teens like zombies. But after the their past, they're going to make a change of heart to the future they want.

Gage is Lelouch Lamperouge from Code Geass

Sunset Shimmer (c) Hasbro