new Handle:g_Timer[MAXPLAYERS + 1];
new g_Kills[MAXPLAYERS + 1];

player_death..
{
     g_Kills[PlayerWinner]++;

     // Тут нужно число правильное подобрать, на счет 0.1 я не уверен, может лучше меньше.
     if (g_Timer[PlayerWinner] == INVALID_HANDLE)
         g_Timer[PlayerWinner] = CreateTimer(0.1, g_Timer_CallBack, PlayerWinner);
}

public Action:g_Timer_CallBack(Handle:timer, any:client)
{
     if (g_Kills[client] > 1 && IsValidEntity(client) && IsClienInGame(client))
     {
         PrintToChatAll("%N сделал мультикил (-%d чел)", client, g_Kills[client]);
     }

     // сбрасываем
     g_Kills[client] = 0;
     g_Timer[PlayerWinner] = INVALID_HANDLE;

     return Plugin_Stop;
}

#include <sourcemod>

new Float:NewKillTime[MAXPLAYERS+1];
new Handle:h_Timers[MAXPLAYERS+1]
new GetNumberMultiKills[MAXPLAYERS+1];

public OnPluginStart()
{
   HookEvent("player_death", Event_PlayerDeath, EventHookMode_Pre);
}

public OnClientDisconnect(PlayerVictim)
{
   if (h_Timers[PlayerVictim] != INVALID_HANDLE)
   {
    KillTimer(h_Timers[PlayerVictim])
    h_Timers[PlayerVictim] = INVALID_HANDLE
   }
}

public Action:Event_PlayerDeath(Handle:event, const String:name[], bool:dontBroadcast)
{
   new PlayerVictim = GetClientOfUserId(GetEventInt(event, "userid"));
   new PlayerWinner = GetClientOfUserId(GetEventInt(event, "attacker"));

   new Float:LastKillTime = NewKillTime[PlayerWinner];
   NewKillTime[PlayerWinner] = GetEngineTime();

   if(LastKillTime == -1.0 || (NewKillTime[PlayerWinner] - LastKillTime) > 0.3)
   {
    GetNumberMultiKills[PlayerWinner] = 1;
   }
   else
   {
    GetNumberMultiKills[PlayerWinner]++;
   }
   if (GetNumberMultiKills[PlayerWinner] >= 2)
   {
    if (h_Timers[PlayerWinner] == INVALID_HANDLE)
    {
     h_Timers[PlayerWinner] = CreateTimer(0.3, TIMER_MULTIKILL, PlayerWinner);
    }
   }
   NewKillTime[PlayerVictim] = -1.0;
}

public Action:TIMER_MULTIKILL(Handle:timer, any:PlayerWinner)
{
   switch (GetNumberMultiKills[PlayerWinner])
   {
    case 2:
    {
     PrintToChatAll("%N Double Kill!", PlayerWinner);
    }
    case 3:
    {
     PrintToChatAll("%N Triple Kill!", PlayerWinner);
    }
    case 4:
    {
     PrintToChatAll("%N Quadruple Kill!", PlayerWinner);
    }
    case 5:
    {
     PrintToChatAll("%N Sextuple Kill!", PlayerWinner);
    }
    case 6:
    {
     PrintToChatAll("%N Septuple Kill!", PlayerWinner);
    }
    case 7:
    {
     PrintToChatAll("%N Octuple Kill!", PlayerWinner);
    }
    default:
    {
     GetNumberMultiKills[PlayerWinner] = 0;
    }
   }
     
   h_Timers[PlayerWinner] = INVALID_HANDLE;
   return Plugin_Stop;
}