what's the most confusing movie you've ever seen?

so I just watched Tenet for the first time and I don't think I've ever been this confused watching a movie before. I feel incredibly stupid right now. I was fine up until the half way point and then I was totally lost and could not follow at all. is it one of those movie where you're meant to watch it more than once to undrestand or am I just really dumb?

what movies have left you feeling totally lost and confused?