Hello,
What version of SEP 12.1 are you running?
Cleanwipe is the best solution, if you are looking only for uninstalling of SEP client (without password)
https://support.symantec.com/en_US/article.TECH213385.html
OR
You could manually uninstall the SEP client as well.
https://support.symantec.com/en_US/article.tech161956.html