1. After the beta ends the SS get vehicles to use from one of Waller's goons.
2.  
3. They then go to capture Ivy from Lex Luthor
4.  
5. Ivy is nine years old and has been revived by Luthor to make antisuper weapons
6.  
7. Ivy doesn't remember Harley and thinks the name "Poison Ivy" is dumb
8.  
9. Waller insists that they put a bomb in Ivy's neck.
10.  
11. Everyone thinks that's crossing a line, except Boomerang who does it anyway to be squad leader or something. Ivy cries and the rest of the SS call Boomerang a cunt.
12.  
13. Flash captures Luthor for brainiac (idk why)
14.  
15. Flash uses Luthor to lure out the SS
16.  
17. SS fight Flash. At some point Luthor is killed WW joins the fight at some point, captures Flash with the lasso. Flash says there is no cure and she has to kill them all.
18.  
19. Boomerang overhears Flash's name as "Barry" from WW but has no idea who that is.
20.  
21. Flash escapes and WW fucks off after mocking the SS for the third time.
22.  
23. Waller insists they kill Flash so Boomerang makes fun of "Barry" on national tv to bait him out
24.  
25. Flash is killed by Boomerang
26.  
27. SS are somehow transported to Earth 2 during this fight
28.  
29. Earth 2 is an earth where Brainiac has already won. The SS there were all killed thanks to Waller.
30.  
31. There they meet Earth 2 Luthor who explains what happened and says he's been in contact with Earth 1 Luthor explaining how to fight brainiac.
32.  
33. Earth 2 Luthor comes back with them to Earth 1. At some point they fight green lantern (can't remember why)
34.  
35. KingShark takes green lanterns ring (does the whole lantern speech) and then someone (probs Deadshot) kills GL
36.  
37. Superman comes and mirrors the scene from the first trailer where boomerang pisses him off and blames King Shark
38.  
39. WW saves the SS and uses something (maybe red sun?) to try to kill superman. It fails but Superman goes to krypton to regenerate. WW dies after giving a speech to the SS
40.  
41. The reason Superman came out is because Waller sent a nuke to Metropolis. The SS cheer him on as he destroys it which unwittingly draws his attention to them.
42.  
43. SS are very sad after WW dies and don't know how they're going to kill Superman
44.  
45. Earth 2 Lex says they need to capture Batman so that he can make something which can kill Superman
46.  
47. The SS use a bootleg Batmobile to infiltrate the batcave.
48.  
49. In the batcave they find Tim Drake's corpse. Who was killed by Batman off screen.
50.  
51. They knock out Batman and miniaturise him to bring him to Luthor
52.  
53. At some point in the batcave they find a video Bruce made explaining how to kill all the justice league members. The SS get bored halfway through and so don't watch the part explaining how to kill Superman. Luthor makes Kryptonite bullets for the SS to use to fight superman
54.  
55. After Batman's usefulness has expired the SS debate over which one gets to kill him.
56.  
57. Harley wins and gives a speech, Batman says it's shit and then dies.
58.  
59. It's implied that Harley makes some kind of batsymbol in Batman's corpse (think like Inglorious Bastards but maybe a little less brutal)
60.  
61. They then fight Superman. Idk much about the fight but it ends with Superman dying (presumably killed by Shark)
62.  
63. Brainiac congratulates the SS for killing the Justice League and offers them great power
64.  
65. The SS use an ice cream van to get inside the skull ship
66.  
67. SS take out brainiac and miniaturise him. They bring brainiac back to Waller and Earth 2 Luthor. Waller congratulates them and says their prison time has been reduced.
68.  
69. Turns out there are 12 other Brainiac's from different universe's the squad have to go and take out though (in post game + seasonal content) Something goes wrong (I think Luthor betrays them) and the story ends.
70.  
71. Besides story the only major discoveries I've made are that the additional playable characters are: Joker, Mr Freeze, Deathstroke, Katana and Killer Croc.
72.  
73. This user claims to have read data mined dialogue
74.  
75. Edit: the user has posted audio of Batman's death confirming its validity.
76.  
77. Massive death spoiler for Kill the Justice League. Do not click if you want to go in fresh!!