I don't think anything can ever top the failure that was the Wii U. It was literally a failure in all regards: Absolutely horrendous marketing, no clear message, the "gimick" of the gamepad which even Nintendo's own teams couldn't find a good use for in their own games that they built the system around, it was slow as shit, had nonexistent third party support, and droughts droughts droughts of no games. Remember when DKC: TF came out and the gamepad screen was just black? And then halfway through the gen they tried to start marketing it like the Wii again with things like Wii Sports Club. It really felt like Nintendo had no idea what the fuck they were doing with that system from the get go. I've never seen a system look so undesirable. Those were dark times, man.
It had some great software but not even that could have saved how badly the system was handled.