what is the most scure password manager?

Any known password manager is a target.

If you have a Linux PC you can create a partition encrypted with LUKS and save the passwords in txt files. Even this solutions has a small risk because when you open a file it might end up in the cache. But it is still safer than Keepass.

Downside. It might take a little bit more than few clicks to access to your passwords. But I suspect that the concern over too many clicks is inflated by the big corporations looking to dumb down their users.