When something really unfortunate has happened.
When something needs to happen asap to prevent annoyance/trouble/fighting because if it doesn't, shit's gunna go down!
Yeh, he was in a fight and got smacked badstyle.
She needs to get out of my face, badstyle.
This is a word often thrown around by Caribbean people (esp. Belizeans) when describing someone who shames someone or goes against his word to the inconvenience or detriment of someone else.
Person A: Man, look at how small that thing is.
Person B: Yea, but it is still is a hell of a lot bigger than my ex-boyfriend's dick.
Person A: BADSTYLE!
Person A: You hear how Jill badstyle Jack?
Person B: No, tell me.
Person A: She ketch belly fo his bredda, then set he up fo mek he think da fi he.
Person B: Real badstyle!