group or individual who brings people trouble and disaster

• 等看到二人手里拿着刀，才知道“好姐妹的男友”已成为自己的灾星。

  It was only when one saw that the two of them were holding knives that one realized that the "boyfriend of one's good friend" had come to spell trouble for oneself.

• 他说我是灾星，都会有不好的运气。

  He says I am a jinx, always bringing bad luck.