I think that anyone with a degree of true super-speed is overpowered. They are very difficult to write and be believable. Only beings with a degree of cosmic awareness or something equivalent should be able to fight them.
The Grandmaster was able to keep pace with Runner and Makkari due to his ability to manipulate space-time. But other than that, it's difficult to see someone like Gladiator or even Quicksilver being challenged without writing them down, or assuming/implying that the character they're up against has super-senses that compensate for speed.