How Secure is VPN over unencrypted wifi networks?

I’ve tried googling similar arguments several times, and all I ever find are people’s opinions and speculation. I want to know if someone has objectively tried cracking passwords and other sensitive data being sent via vpn over an unencrypted wifi network. I personally am not savvy enough to do this – I can capture packets but wouldn’t know where to begin decrypting passwords, etc…

If you know of a site that has done this, or have personally done such work, let me know or please point me in the right direction. Thank you.