Solution:
You can try with this:
RewriteEngine On
RewriteRule ^([a-zA-Z0-9_-]+)/wp-admin$ /wp-admin [L,NC]
It redirect any given path followed by /wp-admin
to yourdomain.com/wp-admin
ex.
www.yourdomain.com/anything/wp-admin
redirect to:
www.yourdomain.com/wp-admin