Originally Posted by Adasunshine
I think she was right when she said at the end that he needs someone to tell him to stop...
Spot on the money I think.
We can see from the way the Doc was going to obliterate the spider folk the embers of that hugely destructive side of the doc. As I said in the thread for me the companion is now the "humanising" factor to the Doctor. Rose (though icky) was perfect for the Doctor to get over the "terrible" events of the time war and re-introduced a moderating effect to the doc.
Without the companion to ground him and to slap him in the face with humanity he'd be the biggest monster of all making the Darleks and the master look like kids in the school yard.