How can I bypass iCloud Activation Lock on iPhone 12 Pro Max without account information?

There is no way to bypass it and that is the whole purpose of having Activation lock in the first place. You have 2 options to prove the device is yours.

• Gain access to the account it is locked too. Only you would know that information and resetting a password may be an option, but you would still need to know the Apple ID email address you used when it was set up.
• Provide the original purchase receipt from Apple or Authorized Apple seller and submit that documentation to have the Activation Lock removed.

Did you purchase the device from a third party? That would explain why you would not know anything about the account it is locked to and if that is the case, the device is just a brick. Hopefully that is not the problem and if it is, then attempting to return it is your only option.