Is has irresistibly a grammatically correct sentence?

"Has irresistibly" is not a grammatically correct sentence. It's missing a subject and a verb that agrees with the subject. Here's why:

* "Has" is a verb, but it needs a subject to act upon. For example, "He has irresistibly..." or "The cake has irresistibly..."

* "Irresistibly" is an adverb, which modifies a verb. It describes how something is done, but it doesn't act as a verb itself.

To make a complete sentence, you need to add a subject and a verb:

* "The cake has irresistibly drawn me in."

* "She has irresistibly charmed everyone in the room."