How can I remove the Akismet Plugin fully from my site?
It is not installed.
Go you your CPanel -> File manager -> inc -> plugins-> delete Akismet from there.
No other files should be deleted or what?
./inc/plugins/akismet.php
./inc/languages/english/akismet.lang.php
./inc/languages/english/admin/forum_akismet.lang.php
That's all files related to Akismet.