You are right when it comes to anything finals Real Madrid is always on there prime and they don't joke with finals they alway force to win regardless of who they are playing with but this time around the team they are playing is really inform and there rival in that matter and they have been defeated twice this season with a very big goal margin and currently Real Madrid defense is not that good and Barcelona has good attackers and finishers so it will be very difficult for Real Madrid to withstand the pressure.
This season Real Madrid always loses to Barcelona. This team has met at least 3 times. Twice in La Liga and once in the Spanish Super Cup final. And yes, in these three matches, Real Madrid always lost. First, Real Madrid lost with a score of 1-2, then Real Madrid lost with a score of 0-4, and finally Real Madrid lost to Barcelona with a score of 2-5. And actually I'm not sure that in the Copa del Rey final we will see Real Madrid avenge their previous defeats. because from the previous match against Real Sociedad we still saw how fragile Real Madrid's defense was. So Barcelona's chances of winning still seem quite big in El Clasico this time.