Not necessarily a series, but Nintendo as a company. They make it hard to boycott them.
Their business decisions are so bafflingly stupid it exceed all logic and reason. They copyright strike YouTubers who upload their music, but they make no efforts to publish the music themselves (besides scant soundtracks here and there). They make upgrades to online services that add not enough that's worthwhile to justify price increase. Will they listen to fan feedback regarding this? No. They ONLY look at sales numbers, which is especially tough on all the content creators who feel pressured to buy it for review/comparison purposes. They cancel online eShops leaving the games to not be sold by the anymore, but when that happens and others emulate them online for others to enjoy (usually without a profit), and that registers as a net loss for them? Yes, I know they can, since that's in their realm of copyright, but they really need to take fan input seriously. I legit wrote a college essay on Nintendo's business practices because of how much sheer stupidity there is
Being a Nintendo fanboy sucks, but there is an upside.
The Switch has tons of great games, whether that be through first party or ports. Sure, the console doesn't have the best capabilities, but it's also portable, and it can play The Witcher 3, Skyrim, and many other breathtaking games nobody would dream of working either on Nintendo or portable hardware. Let's go back to the first party games for a second. Mario Odyssey and Breath of the Wild are some of the best in their respective series, not to mention Metroid Dread, the new Kirby, and WarioWare Get it Together (all of which I need to play eventually). Yes, Witcher and Skyrim are impressive, but the Switch also has Cave Story, Celeste, Hollow Knight, Undertale, a Hat in Time, Stardew Valley, Minecraft, Terraria, Streets if Rage 4, Scott Pilgrim, Fez, Shantae, Ori and the Blind Forest, Cuphead, Rayman Legends, Grim Fandango, 10 kinds of Tetris, The Mega Man, Castlevania and Pac-Man Collections, and of course, Super Monkey Ball Banana Mania.
In short, I love Nintendo as a game developer, not so much as a corporation.