Talking about Real Madrid, they are a team that is a stumbling block for all teams in the Champions League, because they always have their own way of winning.
Actually Real Madrid didn't always win UCL in every season. They also experienced losses and failed to win UCL trophy. But they become very superior if they reach the final round. That's why Guardiola stated that to beat Real Madrid shouldn't be in the final, beat them before they reach the final round.
I usually have this type of thought in me that Real Madrid can only not win the champions league trophy until they are eliminated from the competition. It does not always look easy to eliminate them but it does happen and has happened several times for all those seasons they didn’t win the champions league trophy. What I notice more with them is that, if you want to win them, don’t wait till finals because they’re always at their best in the champions league finals and have only lost few times in the finals for all the times they’ve made it there. So eliminate them before reaching the final if you want to stand a chance to win the champions league trophy.