Foils

A foil is a character who serves as a contrast to another character, usually the protagonist, in order to highlight the differences between them.

Examples

 * 1) Toy Story 3: Woody and Lotso
 * 2) *Similarities: Both serve as leaders of their toy families.
 * 3) *Differences:
 * 4) *Woody prioritizes the well-being of his owner Andy and the other toys while Losto grows to hate his owner Daisy and children in general and treats other toys horribly.

The Overall Reason Why The Trope Isn't So Different

 * 1) It highlights what the hero and villain have in common and how they are different from each other.