I'm interested in responses here because my 5 yr old dd has a similar friend.
I have recently stopped out of school playdates - not so much because of the friend's behaviour, but the mother's lack of action in dealing with it. This has caused a huge argument. I did try to delay the playdates by saying, we're a bit busy this week. But the mother was incredibly insistent that my DD comes round - sometimes twice a week. Sometimes getting down on my DD's level, after I've clearly said "no we can't come" and saying to her, "you'd like to come round and play now wouldn't you".
Her friend will demand to play with whatever my dd has picked up to play with. The mother then launches into how my dd doesn't know how to share. She gives the toy up. Picks up another - and he wants that too. And so it goes on.
He's now following her round the activity tables at school, whining and demanding she gives up whatever it is she's picked up to play with.
He only wants to play his choice of games. My DD does this for a while, then says, I'd like to play my game now. He runs back to his mother crying "she won't play with me". The mother then tells my DD what a nasty girl she is.
He doesn't like her to play with anyone else. My DD describes this as "he tries to make them not like me". How? He tells them I said they were fat. He tells them I said they are boring. When I didn't. He just lies.
It's just really worrying when it's happening to your dc - I really do understand where you're coming from. But like you, this is the first child I've come across of this age whom I really dislike.
I don't know what the answer is. A friend tells me that they change friends a lot over the next few years, gradually finding people they have something in common with, rather than playing with the ones they've just been thrown together with from playgroups.
I'm hoping this is the case for us and you. I can't say intervening has helped much in my case - but it came to a head when the mother started ranting at us in the playground which I had to draw the line at.