Can you file Bankruptcy for a creditor that has already filed a lawsuit against you?

I believe what you're asking is whether or not the debt is dischargeable.  Having a lawsuit filed or a judgment does not change whether or not the debt can be discharged--it only affects what remedies are available to the creditor outside of bankruptcy. Without knowing what the basis of the debt was and more specifics on the facts, I cannot tell you if it would be discharged in your case, but yes you can always file bankruptcy after a lawsuit has been filed, and even after judgment has been entered.