Okay, hum, how to spell it out without being too insulting...ah yes, this is absolute shit and downright insulting.
Not going to tall everything (I'm already too pissed off) so I'm just gonna talk about some stuff.
The JL is killed. The title said it and it happens. And wow how shitty is it done. The Justice League is taken out by the Squad. With guns. Not kidding. Batan, the Arkhamverse Batman, the one and only, is killed from a headshot on his kness next to a bench. Still not kidding. Remember that awesome ending from Arkham Knights? The one with a perfect conclusion for the Bats and part of a genre-defining series of games? Well forget it, THIS is the last Kevin Conroy Batman appearence. Green Lantern is killed with guns (seriously, the whole boss fight is just run around his constructs and then shoot). Flash is defeated in his boss fight via shooting to and in a cutscene by Wonder Woman who just punches him. Superman? You know, the invincible hero? Well, you defeat himby...shooting. Yep, Superman is defeated with bullets and explosives. Then he dies in a cutscene when WW stabs him with kryptonite (and dies herself when Supes has the time to fry her alive with heat vision). But what about the final boss, Brainiac, the 12th level intelligence being who in the comics can overpower Superman and is one of the most dangerous and powerful beings in DC? Well, his boss fight has him turning into Flash and sending mooks and you defeat him...by shooting him. And he dies on his knees when Waller stabs his forehead with a stick. High five, the end. No really, the game ends on a high five.
A few more things. Apparently, the Justice League wasn't formed before this game. This in spite of the TONS of references to the League and its various heroes in Arkham Knight. After defeating GL, King Shark takes his ring and creates a construct with it to break Brainiac's shield. No, the GL ring does NOT work that way but here it does. Flash gets literally pissed on. Again, NOT joking.