While you could file an answer / general denial without asserting any affirmative defenses, I would never advise it. An hour of an attorney's time to review the complaint and relevant documents and facts could reveal defenses to some or all of the claims, and you should assert them.
If the complaint was not "verified" you can just file a general denial. It is not required to file affirmative defenses.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Respectfully, you have a ton of money at risk here. The small cost of at least consulting with a lawyer, if not retaining one, far outweighs the amount you stand to lose if you make a mistake in representing yourself.
This post is for information purposes only and does not constitute legal advice, nor does it establish an attorney client relationship with Mr. Cassara.