I think you just have to bite the bullet and speak to him frankly. The only way to be polite would be to bring him a meal before you tell him. I would also recommend bringing him something like a book or a movie (maybe something that pertains to his situation) or maybe something just to keep him occupied or distracted.
You still need to have that conversation though
When he turns up at your door give a lame excuse, such as "sorry dear, not just now I'm about to do my hair" or "I need to cut my nails and I can't do it if someone is watching".
After a few of these he'll probably get the message.
Well how about some strategically placed pieces of meat and blood around the living room. Then the entire time he is there sit with a large knife, stroking it and smiling at him.
If it was me and i said it politely the first time and the person didnt get it...the 2nd and final time would NOT be polite...
Shut up and quit whining about it....get over it...at least you still have your leg....keep bitchin about it and i will cut the mother f*cker off and shut it up your ***!!!
And even though he may have it removed...this person has whined and complained so much that his brain will likely suffer from "phantom limb"....even though its gone he will still feel pain...a dr may have to retrain him and his brain to realize it is no longer there
Just say "I NEED some space so don't contact me for a while please and I wont be contacting you".