Spoilers for Flash Forward #5 (of 6) by Scott Lobdell, Brett Booth, Norm Rapmund, Evan Shaner and Luis Guerrero below.
Wally West has proven over time that he's the fastest speedster, and perhaps, the fastest being alive. However, his speed has been put to the test in a big way. Wally's gotten so fast, that he just outran the Speed Force itself.
Following his controversial arc in Heroes in Crisis, West ends up being recruited by the cosmic universe protector known as Tempus Fuginaut in Flash Forward to fight against the threats of the Dark Multiverse. In Flash Forward #5 Wally's new path brings him to an Earth where his long-lost kids Jai and Iris West are seemingly trapped. As he tries to free them, his kids are absorbed by dark matter, he's thrown into a temporary dream with his wife Linda Park and a baby Iris. Tempus soon breaks him from that dream, making The Flash really, really angry.
Wally immediately confronts Tempus for using his family to toy with him. Before the cosmic being can explain what's going on, Wally becomes enraged wondering how he could be asked to destroy the planet where he saw his kids. The Flash proceeds to push himself "further and further than anyone has ever moved before." Wally ends up going faster than the Speed Force in what's an insane feat of pure speed.
The Speed Force is the source of Wally's (and every other Flash's) speed. The fact that he can build up so much speed that he can outrun the Speed Force should be impossible. But, when Wally is so desperate and frustrated with his cosmic quest and feels like his missing children are being used to feed Tempus' quest, he becomes faster than he's ever been.
Ultimately, the Morbius Chair stops Wally and gives him a look into his soul and past. He sees that his kids were ripped out of his hands and from reality. Tempus tells Wally there's information in his head that he rejects, like the reason why he needs to destroy the dark world his kids are trapped on - because Wally is the one who created it. The dark world represents The Flash's greatest fears and he's the only one who can stop it.
Wally's quest is clear. He must take on and destroy the dark world formed from his greatest fears. Honestly, the dude can't catch a break. His story has been filled with tragedy. Wally has the chance to do make things right in the multiverse and has to take on his own nightmares to do so. That's a tough task. At least Wally West has unlocked a new echelon of his speed to help him take on whatever comes next.