Negative Tachyons

Negative Tachyons were tachyons that were the antithesis of the Speedforce.

The Flash: Season 5
After some testing of why Nora could not travel back to her own timeline, Wally and Caitlyn discovered she could not go there thanks to the load of Negative Tachyons in her system.

Known people affected by Negative Tachyons

 * Nora Allen