The Flash showcases one of his best skills in Dark Nights: Death Metal Speed Metal #1, and reveals why it's only useful in extreme situations.
Of all Flash's moves, one is so dangerous that it should only be used in the most dire of situations. Dark Nights: Death Metal Speed Metal #1 reveals why Wally West can't often use the maximum application of his abilities.
As one of the fastest men in the DC universe, the Flash family has many secret tricks that allow them to unleash their incredible powers. Due to their connection to the Speed Force and the science behind many of their "Flash facts", Speedsters have been able to pull off amazing stunts like infinite mass impacts and even a limited degree of air running. While the Flash and his allies have their power at their disposal, that doesn't mean they don't have to be careful when using it. As many Speedsters have discovered, the Speed Force can be very relentless, even for Flashes.
As an example, Wally West reveals that there is a power that can give him and his allies a great boost, but also at a great cost. In Dark Nights: Death Metal Speed Metal #1 with Joshua Williamson and Eddie Barrows, Wally is hunted by the Dark Knight, AKA the Laughing Batman because he wanted the godlike Manhattan powers that The Flash had in him. Wally flees for his life along with Barry Allen, Wallace West, and Jay Garrick, as they are hunted by a pack of black lightning unleashed by Blackest Night. With Speed Force depleted, Wally is forced to play an ace. He utters the Speed Force formula, pioneered by Johnny Quick, to stop time completely. Kid Flash notices that his speed is dropping, and Barry points out that this hastened Speed Force's burnout.
Flash's Ultimate Move Is Effective, But Dangerous
The formula that helped Johnny Quick gain speed powers is a great way for normal folks to use speed powers, if they haven't already connected. Someone like Wally or Barry has already been blessed with their connection to the occult phenomenon, there would be no need to say that. However, those with supernatural powers seem to be able to improve their abilities through formulas. Unfortunately, the increased power has a downside that makes it not worth it.
Being able to freeze time if necessary is an amazing ability (and the Flash's savior family situation). But this puts a heavy strain on the Speed Force, which affects not just the speakers of the equation, but all other Speedsters as well. It essentially creates a small amount of breathing room in exchange for a ticking clock that counts down to the time the flash's power fails. It helps Wally save his allies from a gang of vicious speedsters, but could easily lead to their deaths. Freezing time can be a very effective power, but The Flash knows it's only useful in an apocalyptic scenario.