Be there he a tutorial for create a leaderboard kill system in ROBLOX Wiki?
No I don't think so. But all you want to do is create a log system (preferably completely server sided) that logs every time someone does damage to another player. And upon death it either awards to the last player to have entered into the log under the victim or the player who did the most damage. You could set the log to clear entries based on how long it takes a humanoid to heal it's damage.