Continuing the discussion from What's the worst movie you've ever seen?:
This seems worthy to explore as a separate topic. There are so many to choose from. High on my list is Andromeda Strain. Yeah, no wonder you all die, you failed to take any precautions while handling the alien substances.
More recently, a scene in AntMan made me leave the room. The protagonist enters a storm sewer in the parking lot of the building they are hoping to infiltrate, and he comes out of a bathroom faucet inside the building. I believe I said out loud “what the actual fuck?” You can’t access water mains from curb basins because they never connect. Water is a) pressurized, b) sealed, and c) inaccessible without undoing a) and b). Yargh.
Let’s have 'em, the movies that failed hardest at science in your opinion.