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.
Add the fact that you have to protect Tatsuki as well ? It's one of the hardest fights in the game, beaten only by one of the many other times Ulquiorra shows up
The 30th Floor of Bleach Tower. There are extremely powerful versions of Arturo, Seigen, Kenpachi, Soi Fon, Ichigo, Yoruichi, D-Roy, Ulquiorra, Yamamoto, Gin, and Grimmjow, and toward where your characters start, there's a Sky Rift that spews Hollows! Thankfully, to win, you only have to defeat Grimmjow, but he's Level 90, has insane stats, and can Release. Expect most of your characters to die.
The Final Boss deserves mention as well. The boss has numerous tentacles which each have 2000+ HP and are All-element. On top of that, the boss has a Wave Motion Gun that goes across the entire map and can Shock, and just being in the boss's vicinity also causes Shock. Which is highly annoying because being able to use Skills makes the fight go much quicker, and also makes healing easier due to the arbitrary 10-item limit on inventory. And once you actually get to fighting the boss? He hits like a truck and has massive HP. If you have Co-op attacks, it makes things slightly easier, but it still takes a long time to whittle him down.
Expy: Fujimaru is basically a cross between Kyouraku, Urahara, and Ichigo (especially if you chose him as your player character).
Game Breaker: While all Bankais can be abused this way, special mention must go to Byakuya's Bankai S. Kageyoshi combo when leveled up correctly, it is a skill automatically given to Byakuya, so all you need to do is level his bankai and second skill routes, and you suddenly have a hollow killing machine.