@Anish160 you can try to collect extra guest fees (if you normally charge those) or extra cleaning through the resolution center. The guest will undoubtedly be triggered to leave a bad review as soon as you ask. Airbnb may not support you...they often don't. They will likely ask for photos of the party in progress before they believe you. If your guests refuse your request, Airbnb will arbitrate.
I would definitely leave an appropriate review such as the following:
"So and so booked for 6 but at least 14 people arrived for an unauthorized party. Extra clean up was needed. Guest did not communicate their intent to bring so many people to our space. We can't recommend this guest and they are not welcome back. "
Low stars in all categories/would not host again.