Wally West around the time of Morrison's JLA, he seemed at peak power there, and in his solo series.
Blue Marvel, Captain Marvel, Miss America, Spectrum, Black Panther.
No prep.
No BFR.
If we takes into high end feats with no CIS, wally is approachin zoom level
, only 4 kinds of people can beat him
1. reality warpers and toon force
2. characters that zoom can't hurt (juggernaut)
3. characters that can instantly reform themselves (dr manhattan)
4. character faster than him
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If we take in consideration Flash's ability to be predictable and Black Panther's combat skills, the fight ends the moment BP punches Flash into the throat.
But in all seriousness, people are, for the most part, misunderstanding your (simple) question.
Can he?
The answer is of course, yes. It is certainly feasible to do so. With his speed, he can make this entire thread one-on-one.
Morrison's Flash, after all, was the one capable of running through as many battle simulations as needed to find the perfect battle tactic: https://s5.postimg.org/a9y771wev/image.jpg
As someone else said earlier, while in a comic the Flash could lose to the the team, in a forum fight the match would go to the Flash. He is simply so fast that by the time the team could conceivably come up with a solution (note that the OP said no prep), the fight would be long over.
This doesn’t mean speed wins everything every time (and to respond to Carver’s salty ‘Flash defeats the Marvel U in a picosecond, obviously not ...but then again that was just a salty comment from him due to difficulty properly addressing Flash’s speed, for example Hulk cannot just smash ...), but certain high order speed is a uniquely effective power set. It doesn’t make a character invincible...far from it. But it does enable a character to significantly punch above his/her weight.
In short, yes the Flash can solo this team as per the no prep, no BFR stipulations. Morisson’s Flash was one of the more powerful depictions of the character, and has accomplished scaled and complicated feats in fractions of a fraction of a second’s fraction. As cool as the team might be, none of them have a ready solution to that.