Why are Flash and Reverse Flash Enemies?

You see, Eobard Thawne never wanted to be the Reverse Flash.

In fact, Eobard Thawne was one of the Flash’s biggest fans.

But, he came to know that his destiny was to become the Flash’s greatest enemy, opposite, reverse.

This knowledge drove him mad. How could he become the greatest enemy of the man he came to adore and cheer on?

Realizing this, he recreated the conditions in which Barry Allen became the Flash, and turned into the one thing he didn’t want to become.

The Flash’s greatest enemy, Reverse Flash.