[Facerafter]

You can create a killcounter.

pawn Код:

new KillCounter[MAX_PLAYERS];

public OnPlayerDeath(playerid, killerid, reason)
{
       KillCounter[killerid] ++;
       return 1; // Adds 1 to the kill counter of the killer every time he kills someone.
}

While making this... i got confused to how to show the highest player.
Anyways you already got a start here.