Or tried to kill. This is only about the original Scream because I don't care enough for the sequels.

Steve Orth & Casey Becker:
Both killed by Stu.

- Stu had more personal motive to kill those two. (Casey dumped him for Steve.) The only motive Billy may have had is to throw Sidney mentally off, but for that anyone could do and he could easily let Stu do the dirty part. I'm quite sure it was Stu's idea to pick Casey and Steve as the victims. Aldo, see the look in Casey's eyes when she removes the Ghostface mask to see who's butchering her. It is a look of regocnizing the person and regret/shock....

This is an elaborated article based on my comments and posts on couple of fan picks and forum topics here.

"But this is life. This isn't a movie."
"Yes it is, Sid. It's all one great, big movie. You just can't pick your genre."

Billy may not have an outstanding personality as a killer but he certainly has much to give as a whole character. I love him to bits!

The shittier boyfriend: The one that fucks you, dumps you and doesn't even nake you famous, or the one that murders your mom, takes your virginity so he could kill you, and makes you famous? That was just inspired by a line that made me laugh...