The entire film. From dumbed down space-time jargon that is over-explicated all the time to "maudlin truisms and increasingly New Age mumbo-jumbo about the power of love" as one reviewer put it.
There's idiotic stuff like Romily explaining to genius Nasa pilot Coop what a wormhole is as there about to fly into one. There's way too much expository dialogue that gives complete lie to the "show not tell" rule that is especially important in film. The dialogue comes across as a bunch of explanatory monologues, cut up into short little bits to make conversation, often with random and ridiculous questions attached so as to give it a semblance of the natural. Nolan seems to think most of the audience is rather stupid and won't notice just how silly this is, by trying to sneak it into conversation wherever he can, but it just comes across as clunky and irritating, and as though we're sitting through some sort of strange hybridized blockbuster film/really shitty science lecture.