[Pottus]

1.) You need to save the id of the killer of player killed in a variable.

pawn Код:

Example. MyKiller[playerid] = killerid;

2.) You don't want to use IsPlayerConnected() instead what you want to do is check when a player logs out if they are in another players MyKiller variable.
Example.

pawn Код:

for(new i = 0; i < MAX_PLAYERS; i++)
{
    if(!IsPlayerConnected(i)) continue;
    if(MyKiller[i] == i) MyKiller[i] = INVALID_PLAYER_ID;

}

3.) Check for a revenge kill on death

pawn Код:

if(MyKiller[killerid] == playerid)

I hope that helps.