Real Madrid vs Athletico Madrid will be a tough game because Athletico Madrid is in good shape and giving Real Madrid a tough time on the pitch, but in terms of Champions League, Real Madrid always do well and challenge the teams that face them. However, Madrid will perform better and win at home before going to Athletico Madrid's home for the second leg, because if Madrid allows Athletico Madrid to win the first leg, it will be very difficult for Madrid to win. them at home.
Sorry to say if you mean the comparison of ATM and Madrid in La Liga then I agree but this is Ligue Champion which overall Madrid makes this competition the most targeted. That's why they have 15 trophies because when Madrid is in UCL has a different level of motivation than La Liga. Maybe for now it's okay ATM is said to be in good condition but don't forget Madrid is doing it little by little and in fact such conditions are much more dangerous if underestimated.
Indeed, I also admit that Real Madrid is the king in the Champions League with the most trophies compared to other teams in the Champions League. Also, I admit whatever the situation and condition of Real Madrid, but when it comes to Real Madrid's chances in the Champions League, there is no need to doubt because Real Madrid has always managed to overcome tough competition in the Champions League and ended up with the trophy. But at least, I still consider that failure can also happen at any time and thus,any result can still happen in their match later. Because indeed, Atletico is also in a good trend this season, so maybe, Atletico can make a surprise by defeating and eliminating Real Madrid in the last 16 later, I think a result like that can still happen.