I am looking for expressions in English for a child that stubbornly refuses to play with others, for example a group of other children, although they are friendly and inviting and actually would like the one child to join their group, say, out of a sense that it is better to cooperate in a group than to isolate oneself.
Could be a word, or any other expression.
"Spoiler" comes to my mind but I don't know if this is applicable to a situation like above.
I would look for expression that - when used in metaphors to describe the behaviour of powerful protagonists in society (not children!) - may sound ironic or slightly sarcastic.
Note (added later): as commenters below stated that they would refuse answering this question because it was cruel towards children displaying such behaviour I hereby officially declare that I do not intend to use the term(s) with regard to real children. I was thinking of other, less vulnerable entities such as politicians, companies, associations, etc. This is meant for metaphors in newspaper articles.
(By the way, I find it irritating that so many people obviously vote this question down not because it is a bad question but because they presume I was about to abuse children with these terms. Is this called helicoptering?)