$ sudo apt-get remove blast2 

Uninstall blast2 including dependent package

If you would like to remove blast2 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove blast2 

Use Purging blast2

If you use with purge options to blast2 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge blast2 

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 blast2 

See Also,