What is the ruling of Islamic law regarding someone who guaranteed a person to a usurious bank and the guaranteed person then fled? Will Allah punish the guarantor for his dealings with the usurious bank? And what should the guarantor do if another usurious bank offers to pay off his debts?

A Muslim must avoid dealing with usurious banks. Allah has declared war on those who consume Riba (usury/interest). It is not permissible to act as a guarantor for someone who has taken a usurious loan because it is assisting in sin. The guarantor is obligated to pay the debt if the guaranteed person flees. It is not permissible to settle this debt with another usurious loan. The creditor must grant respite to the one in hardship.