So, so, so many times during Resident Evil 6, almost more than times when I wasn't thinking that. But if I have to pick just one example, the snowmobile section in Jake 2. Requiring a lot more precision than the snowmobile controls allow for, and going the wrong way (except when it isn't) or slowing down at all (except when you have to) leads to an instant death and restart the entire thing. Oh, and if your co-op partner messes up, you have to restart the entire thing. I don't know if the AI can mess it up, but I wouldn't be surprised to learn that they can.
That's far from the only example, but it was one of the worst-executed parts of the game, and definitely the most out of place. Even the motorcycle and Harrier sections felt less jarring, if only because RE5's turret section set a precedent for vehicle sections with lots of shooting. A vehicle section with no shooting, instant death around every corner, and really, really imprecise controls was just the absolute worst thing in the game.
Honorable mention: The Agent.