[Fj0rtizFredde]

As I understand you want to add the prefix to the player's name without changing the name?

pawn Код:

//Something like this would work:
public OnPlayerText(playerid, text[])
{
    if(Your admin check here)
    {
        new pName[MAX_PLAYER_NAME], String[128], Prefix[] = "[Admin]";
        GetPlayerName(playerid, pName, 24);
        format(String, sizeof(String), "%s%s %s", Prefix, pName, text);
        SendClientMessageToAll(-1,String);
        return 0;
    }
    return 1;
}

//Or more simple:
public OnPlayerText(playerid, text[])
{
    if(Your admin check here)
    {
        new pName[MAX_PLAYER_NAME], String[128];
        GetPlayerName(playerid, pName, 24);
        format(String, sizeof(String), "[Admin]%s %s", pName, text);
        SendClientMessageToAll(-1,String);
        return 0;
    }
    return 1;
}