Judas was not forgiven, because...

...he didn’t want to be forgiven. 
Judas went to hell because he chose that way: 
he hanged himself. 
According to Holy Fathers, Saint Peter’s sin is bigger than Judas’ sin, with the exception that Peter asked for forgiveness—while Judas himself terminated his possibility for repentance. 
Peter is the first because of his repentance; 
Judas is the last because he threw it away.