Is 100% interest per year on loan illegal?

Yes.Even in the suspension of the Usury Law and the elimination of interest ceilings, the parties are usually unrestrained to specify the interest rates to be enforced on financial obligations. As a general rule, the interest rate acknowledged by the creditor and the debtor are valid upon them. This rule, however, is not without exception.
Currently, the Supreme Court once again dealt with the validity of interest acknowledged by the parties, declaring that:
Stipulated interest rates are illegal if they are unconscionable and the Court is allowed to temper interest rates when necessary. In exercising this vested power to determine what is iniquitous and unconscionable, the Court must consider the circumstances of each case. What may be iniquitous and unconscionable in one case, may be just in another.

In your case, 100 % interest per annum is considered unconscionable and  illegal.