Windows 10 make UAC always require password

This is controlled by the registry entry here:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]

And you want the value of:

"ConsentPromptBehaviorAdmin"=dword:00000001

Source

ConsentPromptBehaviorAdmin's value reference

An even simpler or easier way is once you find the Value name: block, "ConsentPromptBehaviorAdmin" go to the block below which is Value data: and change the number to a "1". It gives you the same result.

ConsentPromptBehaviorAdmin

This key defines the User Account Control behavior for system administrators. The default value is set to prompt but do not require credentials to be entered. Here are all possible values:

• 0: A value of 0 allows administrators to perform operations that require elevation without consent (meaning prompts) or credentials (meaning authentication).
• 1: A value of 1 requires the admin to enter username and password when operations require elevated privileges on a secure desktop.
• 2: The value of 2 displays the UAC prompt that needs to be permitted or denied on a secure desktop. No authentication is required.
• 3: A value of 3 prompts for credentials.
• 4: A value of 4 prompts for consent by displaying the UAC prompt.
• 5: The default value of 5 prompts for consent for non-Windows binaries.