global void execute(Database.BatchableContext BC, List<Account> scope) {
  List<Account> toDelete = new List<Account>();
  List<Account> toUpdate = new List<Account>();

  for (Account a : scope) {
    if(a.bad_account__c){
      toDelete.add(a);
    } else {
      toUpdate.add(a);
    }
  }
  update toUpdate;
  delete toDelete;
}
