House of Cards definitely adhered to the law of diminishing returns over time and it eventually became more shocking when a few episodes went by without there being some sort of major twist or revelation, desensitising viewers. Both Frank and Claire had become quite one dimensional by the time that season five rolled around, frequently seeming to be diabolical for the sake of it rather than for the 'greater good' in the pursuit of their ambitions.
It has the highest body count of any season, but Tom Yates had long become a joke by the time Claire poisoned him, his schoolboy-like fawning over her having become more and more ludicrous with each passing episode. Aidan Macallan (Damian Young) and Leann Harvey (Neve Campbell) never felt like more than bit-part players and the former's Edward Snowden-esque arc felt rather forced.
On the living front, Will Conway (Joel Kinnamon's) eventual meltdown in the face of Frank's employment of voter suppression and terrorist activity to manipulate their election seemed very out of character even if it had been gradually hinted that he wasn’t as perfect as he seemed, whilst several new forgettable additions to the cast (such as Alex Romero and Sean Jeffries) couldn't even make the cut for season six.
The ending was admittedly intriguing, though it seemed farfetched that Frank would engineer his own downfall to accelerate Claire's career. Ultimately we’ll never know how this was supposed to pan out given the Spacey situation.