I'm not sure how have you written your Essay. However, a good achievement/accomplishment essay is usually a mix of the following:

1. Personal accomplishment (1 example)
2. Professional accomplishment (1 example)
3. Community service accmplishment (1example)

So, if you follow the above pointers, there is no way that your achievement/ accomplishment essay can look like a summary of your resume. All you are really doing is - picking that ONE bullet point from your Resume and telling the background story in your essay.
Your resume usually covers your professional part, this is why a personal accomplishment adds a new facet to 'you' in your Essay. Personal accomplishment can be related to sports or academics.

Hope this helps.
Good Luck!