Does the debt of a debtor become religiously nullified if he declares bankruptcy, and does that affect the validity of his future Hajj?

If the loan is interest-based (usurious), it is not permissible to enter into it. Declaring the borrower's bankruptcy does not nullify the debt. The one who has engaged in an interest-based loan is obligated to repent and return only the principal amount, without the interest. If the lending party is a private entity, the debt is not nullified by bankruptcy unless the entity absolves it. It is permissible to use stratagems to nullify the interest, due to its unlawfulness. However, if the lending party is a governmental entity and the country's law permits it, then declaring bankruptcy is permissible as long as the borrower is truthful about their inability to repay, as the law considers this an absolution from the state.