[Konstantinos]

pawn Код:

if(pInfo[killerid][pKills] == 10)
{
    pInfo[killerid][pRank] = 1;
    format(str,sizeof(str),""chat""OLD_ADMINCMD" [RANK] %s(%d) has been promoted to rank: Private 1",PlayerName(killerid),killerid);
    SendClientMessageToAll(-1,str);
}

The problem was: PlayerName(killerid)),killerid

Also the id is integer, so it'd be %d, not %s.