Re: Who can kill...
DSM Kabuto: IDK, Minato maybe :shrug: his speed+ sealing techniques should be able to do at least a decent job against his Edo's, don't know how he'll handle the Genjutsu though... maybe he could summon Gamabunta or something. Kishi just made Kabuto too damn strong.
Edo Madara: Not even gonna try this one. I don't see anyone defeating Madara 1v1 without a hell of assistance from plot no jutsu.
Obito: Pretty much the same, Kishi made that guy waaayyy too strong, at this moment, I think the only one who stands chance coul possibly be Naruto, but that is still pretty far-fetched.
In my opinion, the one who stands the best chance of beating any of those 3 would be the other 2 on the list (although Edo Madara would probably beat the other 2)