These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Anticlimax Boss: In SB3, before the expansion, Muneshige is hard to beat even while weakened, but the Xavi tank can be destroyed in secondsnote otherwise, it's pretty much inoffensive if you stay directly in front of it, provided it isn't singing while you do that and Sorin himself dies after one hit.
Motochika and Motonari were popular NPCs that got promoted into playable characters in the second game. From the second game to the expansion pack, Kojuro, Nagamasa and Oichi. But mainly Kojuro (the one who spawns the most fanart between those three). And there was much boo-ing when he got Demoted To NPC.
And special mention to Oichi. Mind you, this is a series dominated with pretty and manly boys, but the Oichi fanbase is very very solid when compared to other female characters, which includes her being the only playable female in the fighting game and returning in 3.
Mitsunari, while actually being a main character in 3, proves to be so popular that he took over Yukimura as the poster boy as of Sengoku Basara 4.
According to popularity polls, the most popular newcomer in 4 is Matabe, despite the comparatively little focus he got in-game. In fact, one popularity poll had him rank 5th out of every playable SB4 character, behind only Mitsunari, Masamune, Ieyasu, and Yukimura.
Ho Yay Shipping: Unlike the Dynasty Warriors series which has a good share of both yaoi and straight doujins, SB is practically flooded with yaoi (with Masamune/Yukimura, Kojuro/Masamune, and Motochika/Motonari being the most popular) with the occasional Oichi/Kasuga hentai. Makes sense as Sengoku Basara doesn't have many female characters.
Macekre: The first game was called Devil Kings in the U.S, the producer attempting (and failing) to make a Darker and Edgier version.
That One Sidequest: From the third game, defeating and collecting all the fugitives. You have to equip a special bodyguard in order to find them, they have a habit of popping up out of nowhere and disappearing just as quickly, and hit surprisingly hard with a strong defense.
They Changed It, Now It Sucks: Shortly before SB3 came out, many fans were baying for Kobayashi's blood for overloading the game with NPCs. Some still are.
Things improved with Sengoku Basara 3: Utage where many characters (including Kojuro, Tenkai and Matsunaga of all people) returned as playable characters.
Akechi Mitsuhide is depicted as a particularly depraved madman when he goads Nobunaga's brother-in-law, Azai Nagamasa, into fighting the hotblooded hero Date Masamune. Mitsuhide diverts a squad of riflemen to fire on his own allies, having also brought Nagamasa's wife Oichi along. He ostensibly allows her to try to warn her husband before having him shot in front of her and relishing her pain. Mitsuhide is a vicious killer as well, serving Nobunaga only because it allows him to satisfy his bloodlust on the innocent and any warriors he finds. After the first season, he seeks to resurrect the Demon King, wanting nothing more than to watch the world burn.
Nobunaga himself leads a hideously brutal campaign of conquest across Japan without care for the innocents who suffer in his wake. After Oichi is broken, Nobunaga keeps her enslaved to his will and has no issues killing her himself. Despite his wife Nohime's devotion to him, he thinks of her as nothing more than a disposable pawn. Referring to himself as the Demon King of the Sixth Heaven, Nobunaga thinks he has a right to do whatever he pleases to those 'weaker' than him and will happily kill every peasant in Japan if it brings him closer to ruling it.
And manly bonding sessions consisting of screaming names while punching each other in the face.
One-Scene Wonder: Kennyo, Yoshihiro, Xavi, and Itsuki in Season 1. The first three while they're slain by Nobunaga's men. Yoshihiro is back on his feet in Season 2.
Seasonal Rot: Judge End. The series is receiving a lot of criticism for its inferior animation when compared with Sengoku Basara and Sengoku Basara 2 by Production I.G. In addition to cutting the action back to a fraction of its former glory, introducing several annoying and useless characters and replacing the rocking soundtrack with vapid ear torture. The DVDs also got poor sales in comparison.