Spoilers
season 3 was.....different. Claire and frank weren't working as a dynamic team like usual. The large focus on stamper was anticlimactic.
Episode 11, the debate, was so strong, but they didn't follow up with it with a visible reaction from frank....
Claire resigned from the UN, and we never heard from Russia again. Claire becoming a UN embassador was silly in the first place, it wasn't realistic.
Finally, the strength that they both showed to each other in the first two seasons was non existent, it didn't make sense.