Flashpoint (Earth-1: Pre-Crisis)

Flashpoint was an alternate timeline created by Barry Allen.

Creating Flashpoint
After defeating Zoom, Barry Allen traveled back in time to the night of his mother's murder and prevented the Reverse-Flash from committing the crime. Allen created an alternate timeline where both of his parents were alive, and he was able to live a normal life without operating as The Flash.

Restoring the Timeline
He soon realized the consequences of his actions and how it jeopardized the lives of those close to him. With the help of the Reverse-Flash, Allen returned back in time and allowed the former to murder his mother, seemingly resetting the timeline.