Account executive are mostly responsible for the more practical parts of the advertising jobs (ie leaflets, distributions, adaptations of materials from different languages, making sure the client is always happy even if it includes a fluffing). They answer to the respective account supervisor and/or to the client service director/account director in short words primarily compromised of yes. That depends on the country and on the account you are working for. In Spain for example, an account executive could probably develop very important campaigns on his/her own which the Account Supervisor or Creative Director will later take credit for.
Who do I have to kill to get this job done. The account executive