Zelda: Tri force heroes. Not a bad game but not great either. Pretty fun in multiplayer, if you actually manage to abide to the games strict rules of 3 players, but alone its pretty bad. Getting all these single player checkmarks was true hell.
Monster Hunter: Generations/Ultimate. Hate the styles, hate the arts, hate the deviants, and just the general style of the game. Doesn't help that the game pops off with a idol themed credits segment instead of the Diva.
Smash: Smash 4 wii U. The wii U version ended up with the worse modes and stage selection, and just the general new characters in 4 didn't do it much for me.
Dark Souls: 2. Combat feels very stiff, and there is a LOT of artificial difficulty going on in this one, especially in new game +. Adding enemy hordes at ever corner is not good gamedesign.
Mario: NSMB, in particular 2. The whole coin gimmick is played very badly, and is literally just for a new title screen, that mixed with the very boring NSMB aesthetics, and boring powerups, makes this easily the worst.
Starfox: Command. Terrible story, very boring gameplay. Every mission feels the same.
Dragon Quest: So far I've only played up to 1-6 and 9, and the worst so far is 9 by far. Terrible 3D graphics, boring story, and just a very tedious game in general. All those quests in the game require you to do some real tedious stuff.
Kirby: Star allies. I know kirby is easy, but this game basically plays itself. Using the partner system, which is needed for the secrets in the game, makes the game a terrible experience in single player.
Metroid: I want to say Other M, but for viarity sake I'm gonna say a game thats almost just as bad, Hunters. Single player is very boring and not even worth mentioning, and the major selling point, the multiplayer, was just ruined by glitches or cheaters since day one. Thats and the controls are pretty annoying.
None of those I would say are terrible or even bad games honestly, except Hunters and maybe star allies.