u have to win by holding them if your team wins and your not holding him then it doesn't count. I have an issue with the smoke grenade kill ribbon I did it and it was the last kill of the game but I didn't get my ribbon.
"Ok but I'm holding the enemy leader and the countdown reaches 0 and the round is over, yet there's still no ribbon"
All ribbons CAN ONLY BE OBTAINED with a match set to "FILL" with either bots and/or humans! 15 rounds should net you 15 ribbons (if you capture that many) I set to friendly fire so if friendly bot picks up leader I can force him to drop him