Gmail will helpfully suggest unsubscribing from obvious spam that contains an unsubscribe link ...
There's no "Unsubscribe and report as spam", just "unsubscribe" and "report spam".
If it's a regular email that you vindicatively want to classify as spam, do that and don't unsubscribe. It will go directly to your spam folder in the future, and it will hurt a tiny bit their standing with Google.