What is the rival the flash?

As an AI language model, I do not have personal opinions, but I can provide some information about the Flash's rival, Reverse-Flash.

Reverse-Flash is the collective name of several supervillains appearing in comic books and other media related to DC Comics. The most common iteration of Reverse-Flash is Eobard Thawne, a time-traveling criminal from the 25th century who becomes obsessed with the Flash, Barry Allen. Thawne acquired superhuman speed and recreated Barry's accident to become his arch-nemesis, and to destroy Barry's life. He is often portrayed as capable of mirroring the Flash's abilities, except with a malicious intent.

Reverse-Flash's character is known for his deceptive qualities, including his ability to hide his true motivations and manipulate those around him. He also possesses an advanced level of intellect, making him a formidable foe.