String nVar = 'A%';

Map<String,EntitlementContact> MapNewEnTlCont = new Map<String,EntitlementContact>();
Set<String> setEntitlementIds  = new Set<String>();

List<EntitlementContact> NewEnTlCont = new List<EntitlementContact>();
List<Account> AccList = [Select id from Account where name like :nvar];
List<Contact> ContactList = [Select Id,Email, Accountid, account.name from Contact where id not in (Select ContactID from EntitlementContact) and AccountId in :Acclist];

System.debug(LoggingLevel.Info,'** Contacts without entitlement..:' + ContactList.size());
List<Entitlement> EntitlementList = [Select id, Accountid from Entitlement where Accountid in :AccList];
System.debug(LoggingLevel.Info,'** Account entitlements ..:' + EntitlementList .size());

For (Contact Cnt:ContactList){
    for (Entitlement Ent: EntitlementList){
            EntitlementContact newEntCnt = new EntitlementContact();
            if (Cnt.accountid == Ent.accountid){
                newEntCnt.ContactId = Cnt.id;
                NewEntCnt.EntitlementId = Ent.id;

               String key = cnt.id + ':' +  Ent.id ;
               if (!MapNewEnTlCont.containsKey( key )) {   // no duplicates here according your own test
                  MapNewEnTlCont.put( key ,  newEntCnt );
               }
            }
    }
}
System.debug(LoggingLevel.Info,'*** ** *** New records ...: '+NewEnTlCont.size());

//** search existing keys reading EntitlementContact based on the read Entitlement Ids in the loops
List<EntitlementContact> ExistingEtlCnt = [select ContactId , EntitlementId from EntitlementContact where EntitlementId in :setEntitlementIds];

//** remove the existing keys from the map
for (EntitlementContact ect : ExistingEtlCnt ) {
    String key = ect.ContactId  + ':' + ect.EntitlementId;
    MapNewEnTlCont.remove( key );
}
List<EntitlementContact> NewEnTlContIns = (List<EntitlementContact>) MapNewEnTlCont.values();
System.debug(LoggingLevel.Info,'** Records to insert into EntitlementContact ..:' + NewEnTlContIns.size());
//** Below loop can be used to check individual Id's
//** For (EntitlementContact Cins:NewEnTlContIns){
//**     System.debug(LoggingLevel.Info,'** ContactId:' + Cins.ContactId);
//**     System.debug(LoggingLevel.Info,'** EntitlementIdId:' + Cins.Entitlementid); 
//**     System.debug(LoggingLevel.Info,'** ---------------------------------');
//** }

//** DML statement to write distinct rows to the table (EntitlenentContact)
Database.SaveResult[] srList = Database.insert(NewEnTlContIns, false);
//** Iterate through each returned result
for (Database.SaveResult sr : srList) {
    if (sr.isSuccess()) {
        //** Operation was successful, so get the ID of the record that was processed
        System.debug(LoggingLevel.Info,'Successfully inserted EntitlementContact. ID: ' + sr.getId());
    }
    else {
        //** Operation failed, so get all errors                
        for(Database.Error err : sr.getErrors()) {
            System.debug(LoggingLevel.Info,'The following error has occurred.');                    
            System.debug(LoggingLevel.Info,err.getStatusCode() + ': ' + err.getMessage());
            System.debug(LoggingLevel.Info,'EntitlementContact fields that affected this error: ' + err.getFields());
        }
    }
}