If you fail to answer the lawsuit and you do not go to court, the credit card company can still get a default judgment against you. Even if you go to court, they will probably win a judgment against you unless you have a legitimate reason for not paying (other than the fact that you don't have the money to pay). It doesn't matter what your financial situation is, a judgment can still be entered against you. The reason for this is that creditors know that in the future your financial situation can improve. When it does, they can use the judgment to collect from you: liens, garnishments, etc.

You can still go to court. Perhaps you can work out some kind of payment plan.  

it is always worth it to go to court when sued; that gives you a chance to tell your side of the story and possibly reduce what you owe, get a feasible payment plan, or prevent some of your assets from being seized--or at least have more warning, if that's going to happen.

The creditor can take you to court. If they win, they can get a judgement against you. If you ever have money, they can use that judgement to try to seize some of it.

If you have no money and $25k of debt, you might want to consider bankruptcy. You should consult with a bankruptcy attorney; many will offer free or reduced cost initial consultations.

If you cannot work out a payment arrangement then you will have to go to court.  There are, however, several defenses that you can argue.  For one, the debt itself.  Your creditor needs to validate it. 

For example, if you believe that the amount of the debt is incorrect, you have the right to dispute it.  The plaintiff must prove that the principal, interest, collection costs, and related fees are not only correct but also agreed to in your contract and properly charged.  In fact, you have the right to your see original contract, account statements, and purchase receipts.

There are several other defenses that you may want to try and assert as well.  I'm providing you with a link to a site that will explain further.  It is for NY courts but the general defenses are the same (certain time requirements and other specific factors will differ) and it will give you a good idea as to how to proceed in court:  http://www.nedap.org/hotline/defenses.html

Also, as previously suggested, you could file for bankruptcy.  Not knowing more particulars of your financial situation it's hard to say if this is a good option for you.  However, you may want to consider it. If so, here is a link to a site that will explain the basics of bankruptcy: http://www.uscourts.gov/bankruptcycourts.html