$ sudo apt-get remove p7zip 

Uninstall p7zip including dependent package

If you would like to remove p7zip and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove p7zip 

Use Purging p7zip

If you use with purge options to p7zip package all the configuration and dependent packages will be removed.

$ sudo apt-get purge p7zip 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove p7zip 

See Also,