Even though PSG has not won the UEFA Champions League trophy, they are a team to be afraid of when playing against in the UEFA Champions League. In the modern-day UEFA Champions League, it is only Real Madrid that has won the UEFA Champions League back-to-back, so it will be a little bit hard for Manchester City to follow Real Madrid's full steps.
Who scared with PSG lol, it just the fans that think they're strong because they can dominate in Ligue 1. PSG isn't a strong club, yeah they can beat Aston Villa, Dortmund, Roma, or any other mediocre clubs in top domestic leagues, but it's not enough to beat Bayern Munich, Inter, Real Madrid and Manchester City.
Imagine if Mbappe leaving PSG, I think people will stop favoring PSG in International league.