If an employee has a guarantee in employment agreement, can we terminate the agreement at a lower cost or no cost?

If by "guarantee" you mean employment for a fixed term, and there is no early exit termination clause, then no, you cannot terminate at no cost (unless you have just cause to do so). I highly recommend that you connect with an employment lawyer at the number below how to best to discuss a termination, if possible, and how to limit your exposure going forward with other employees.