Forgetmenot
Hope Summers
Rogue
It would go like this:
1) Fight starts. Rogue gets KOd instantly (but not killed, since Superman et al. do not kill when in character). Forgetmenot and Hope are safe because team DC isn't aware of their presence due to Forgetmenot's power (which Hope also automatically possesses due to their proximity).
2) Hope walks to Flash, and absorbs his powers (she's using Rogue's powers for this since her own can only copy mutants).
3) Hope instantly absorbs the powers of Superman and Wonder Woman by using Flash's speed.