How to fix .htaccess corrupted

Try reverting back to the default .htaccess file with the following code:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

If you’re using some other “flavor” of WP (e.g. multisite) view the htaccess docs on the Codex for the appropriate .htaccess setup.