I'm pretty sure getting one kill then backing out won't get you banned because it would look like you realised it was a hacked game then left.

People are going to wish they never got into these lobbies after they get banned.

I got in one over the weekend. I didn't want to be banned and I don't think I will because of what I did...

1) I only got one kill and left immediately
2) I didn't do it more than one time
3) I got on Activision support and talked to a guy on the chat and told him how I accidentally got in a lobby and isn't realize until I got a kill. He told me that if I left immediately I should be fine. He then said if I do get reset or banned to contact activision and I should be able to get it reversed