killjoy:
(plural: ‘killjoys‘; for the right pronunciation, please click here)
a person who spoils the pleasure of other people – ‘kills the joy of others’ – either by disturbing their peace or party, or causing some problem or difficulty;
a spoilsport,

a killjoy spoiling the fun of some teenagers
My aunt is a killjoy, always raising objections to the most enjoyable games we like to play in the twilight.
There are all types of killjoys in educational and political institutions who seem to take great pleasure in seeing others being disappointed at losing the fun and freedom.
Some people believe that religious scriptures and clergy are a type of killjoys who after enjoying their share of fun when they were young now try their best to prevent the others having it.
Some killjoys like the ones in the council houses who ban ballgames in parks for fear of children getting hurt may be tolerated, but some killjoys who behead youngsters for participating in music festivals and parties are not just killjoys but a really horrible bunch of killers!
