Marshadow: Do Not Ban
I feel marshadow, while powerful is a not broken.
Many see the ability to steal boosts via spectral thief as a game changer. However, any good set-up team Zygarde, CM Mons, etc. should have redirection or the ability to outspeed and KO. Additionally, things like koko, scarf lele, Deoxys and skymin can all outspeed and do massive damage/KO marshadow.