ok this is how it goes... minato loses to both Itachi and/or Nagato so minato is out of the picture.
Itachi vs Nagato
Nagato brings out his summonings straight away and Itachi is caught up dealing with them for a bit, weakening him. Then Nagato either uses ultimate Shinra tensei to blow itachi and his susanoo across the battlefield or uses bansho tenin to rip Itachi out of his susanoo. Amaterasu and any other attacks from Itachi are absorbed or deflected by either shinra tensei or absorbed by preta paths ability
oh no! Itachi uses sword of totsuka!! oh wait, nagato just deflects it with a ST.
. Even without half of these techs, Nagato simply outlasts Itachi
Nagato>Itachi>Minato, this is the way it has always been
Itachi vs Nagato
Nagato brings out his summonings straight away and Itachi is caught up dealing with them for a bit, weakening him. Then Nagato either uses ultimate Shinra tensei to blow itachi and his susanoo across the battlefield or uses bansho tenin to rip Itachi out of his susanoo. Amaterasu and any other attacks from Itachi are absorbed or deflected by either shinra tensei or absorbed by preta paths ability
oh no! Itachi uses sword of totsuka!! oh wait, nagato just deflects it with a ST.
. Even without half of these techs, Nagato simply outlasts Itachi
Nagato>Itachi>Minato, this is the way it has always been