WARNING: The following article contains spoilers from The Flash #775, on sale now.
While the Flash is usually one of the most celebrated heroes in the DC Universe, all of Central City just turned against him thanks to the corrupting influence of Eclipso's glaive. The powerful artifact amplified the latent negativity inside people, heroes and villains alike in everyone in its vicinity except Wally West.
In The Flash #775, by Jeremy Adams, Fernando Pasarin, Matt Ryan, Jeromy Cox and Steve Wands, Wally faced several superpowered characters, notably including his new boss, Mister Terrific. Amplified by his own personal frustrations with Wally, Terrific attacked and said that he was slightly terrified of the potential Wally possessed, commenting that he might even be stronger than Superman thanks to his unique connection to the Speed Force. Considering just how smart Mister Terrific is, that statement carries a lot of weight. Wally appears to genuinely be more powerful than Superman, which may explain why Mister Terrific has involved himself more in Wally's life lately.
As the Eclipso-influenced Mister Terrific explained, he attacked Wally because the Flash was simply too dangerous to be left alive. The potential power he has due to his special connection to Speed Force means that Wally has a scary amount of potential power, and the Flash already received a new boost to his abilities due to his recent adventure traveling through the Speed Force.
Beyond running at incredible speeds, Mister Terrific fears Wally because his powers are virtually limitless. They defy the laws of physics, potentially setting him up to single-handedly solving societal issues on a global scale. Wally probably has enough power to break the natural laws that bind reality in any way he can imagine. Mister Terrific even states that there is a 65 percent chance that Wally will one day destroy the world with his unknowable amount of power. It may sound like a stretch to justify the act of trying to kill him at the moment, but there is evidence to suggest that Wally's potential power is precisely what Terrific thinks it is.
Wally has a more unique connection to the Speed Force than any other speedster in the universe. It has already been established that Wally is faster than Barry Allen and the fastest being in the multiverse. And unlike the other speedsters, Wally possesses a mainline connection to the Speed Force and can never truly be cut off from it. Other speedsters like Barry merely draw power from the Speed Force, they don't have the same bond with it that Wally does. This allows Wally access to other powers that most speedsters don't have, such as sharing or even taking away speed.
Naturally, Mister Terrific's concerns that Wally, whose powers are greater and the true upper heights of which have not been explored, aren't unfounded. Wally's powers have the potential to have even greater consequences than Barry's if mishandled. And he's already been at the center of several major events that defined the shape of reality like Heroes in Crisis and Dark Nights: Death Metal.
This might explain why Mister Terrific has hired Wally as Michael Holt. He has always been a generous person by nature and hiring Wally was as much about providing him with a stable job as anything else. However, he wouldn't be Mister Terrific if he didn't consider all the angles. Properly applied, Wally's power could potentially change the world and solve issues that would otherwise take decades to deal with. Considering how bad actors have tried to manipulate Wally or misuse his power in recent history, Mister Terrific can also keep a close eye on Wally to make sure that his power stays in his own hands.