1) Coddles wine 2) Cousin of a wet blanket 3) Fictional criminal 4) Kill-joy 5) Misery 6) Party pooper 7) Persona non grata 8) Saboteur on a petty level 9) Unwelcome person 10) Wet blanket 11) Wet blanket, often 1) Fusspot 2) Kill-joy 3) Killjoy 4) Stick in the mud 5) Worrier 6) Worrywart 
Spoilsport is a fictional mutant character in the Marvel Comics Universe. Her first appearance was in Generation X #53. ==Fictional character biography== Spoilsport was born an advanced generation mutant and is the younger sister to the mutant Dragonwing. She became a member of the Rising Sons with her brother, Nightwind, Jet-Black, the Sign and T...
[n] - (informal) someone who spoils the pleasure of others
killjoy noun someone who spoils the pleasure of others