Now, you'll be able to see the full-size profile picture. Right-click on the picture if you're on a computer or tap and hold the picture if you're on a mobile device. A menu will appear, offering you the option to download the image. Click on 'Save image' or 'Download' to save the Instagram profile picture to your device.
And that's it! You've successfully downloaded an Instagram profile picture without the need for any external websites or apps. Please remember to respect the privacy and terms of use of Instagram, and only download profile pictures for personal use or with the owner's consent.