Real Madrid are one of the best teams in the world right now if not the best. So an experienced club like Manchester City with an experienced manager like Pep Guardiola would not even dare to underestimate a club like Real Madrid. Pep Guardiola once said in an interview that Real Madrid is the team he is most scared to face in the Uefa Champions League because they never give up. They got that mentality in them. So even thinking that Manchester City will be underestimating Real Madrid is pretty silly and funny.
Even though last season Man City managed to humiliate Real Madrid in the first leg 1-1 at the Santiago Bernabéu and won 4-0 at the Etihad, that doesn't mean they can underestimate Real Madrid's strength this season. Agree with you, underestimating Real Madrid is ridiculous because Real Madrid is a big team and has a high mentality, especially in the UCL league competition they are king.
Indeed, Pep Guardiola is a coach who is a genius in various strategies, but this season I am not really sure whether Man City will qualify for the semifinals, because Real Madrid this season has been very dominant in the UCL and La Liga. However, this will be a very good match for us to look forward to, actually I want to say that these two teams should have faced each other in the final but unfortunately they have already faced each other in the quarter-finals.