Breaking the Fourth Wall

Without a doubt the hardest achievement in the meta. DPS is not going to be a massive concern because you're going to push the fight all the way to the 'berserk' so I'd recommend as many healers as needed so you can largely ignore all mechanical damage. Don't worry too much about having a safe lane or positioning players to only take 1 stack of the DoT etc. You can just bring lots of healers and ignore all the damage and focus on the wall placement.

To give you a bit of a rundown, there are 6 lanes and the walls can safely stack up to 5 rows of wall per lane (a 6th wall in one lane will equal a wipe).

Each cycle, the boss will mark for walls 3 players, then 1 player, then 3 more players, giving you a total of 7 walls. Then you will get 4 players with the knockback, allowing you to destroy 4 walls.

First, we had the first 4 walls stack in Lane 1 and the remaining 3 in lane 2. Then with the first set of knockbacks, we smashed the 4th wall in Lane 1 and just avoided walls with the other 3 knockbacks. For the second cycle, we built up 4 walls in Lanes 1, 2 and 3 and used 3 knockbacks to destroy the 4th wall in each of those. For all subsequent cycles, we were able to destroy a 4th wall in Lane 1, 2, 3 and 4 with all 4 knockbacks.

This meant our cycles for the achievement tally looked like this for number of 4th walls destroyed: 1 -> 4 -> 8 -> 12 -> 16 -> 20

By the end of the 6th cycle, we had almost every lane full. You might be able to squeeze in a 7th cycle for another 2-3 breaks if needed. After the 7th cycle it's 100% going to hit 6 walls in a lane and the boss will kill the raid with berserk.

Make sure you bring the boss to ~10% and then stop damage until you've got your 6th/7th cycle with all 18 breaks... then nuke it hard before you run out of space!

Edit: The following solution cannot be used anymore due to the addon changes made in Midnight expansion.

If you want a bit of easier time on this boss and you are familiar with Liquid Manaforge weakauras (make sure everyone has the same version, see wago for marker placement, etc. normal raid stuff) you can use this mrt note (its only for 6 rotations). Tested it today with my guild, works perfect, no need to call anything, just follow your marks.

liquidWallStart
+ 0 0 0 1 1 1 (3)
T 6 (3)
+ 0 0 0 0 2 1 (3)
- 2 1 1 0 0 0

+ 0 1 0 1 1 0 (3)
T 6 (3)
+ 0 1 0 2 0 0 (3)
- 0 1 0 1 1 1

+ 1 1 0 1 0 0 (3)
T 6 (3)
+ 0 2 0 0 1 0 (3)
- 0 1 0 1 1 1

+ 1 1 0 1 0 0 (3)
T 6 (3)
+ 2 0 0 0 1 0 (3)
- 0 1 0 1 1 1

+ 0 1 1 1 0 0 (3)
T 6 (4)
+ 0 0 2 0 1 0 (4)
- 1 1 0 0 1 1

+ 1 1 0 1 0 0 (3)
T 6 (4)
+ 0 0 2 0 1 0 (4)
- 1 1 0 0 1 1
liquidWallEnd

I just did this in a pug group and I was the raid lead and was calling out where everybody went on discord. I did look at these comments and it helped me a bit but I want to make this comment really simple. I did this on normal difficulty and I would not advise doing it on heroic/mythic because the stacks might not be able to be healed through. You want raid lead to not wear any gear go dps spec and pull boss and die. You want 6 markers going across orange yellow purple blue green red (1 to 6) and start at orange working your way towards red. So here is the order cause its all cycles and one cycle is 3 wall creates 1 wall create (from the tank) 3 wall creates and 4 wall breaks......4 combos = 1 cycle......you will need AT LEAST 6 cycles to do this so don't panic going OVER 6 cycles as that is the MINIMUM......ok here is the order, I wrote this down on a piece of paper as raid lead so I did it the old school way....
CYCLE 1: 3 orange (non tank) THEN 1 orange (tank) THEN 3 yellow (nontank) THEN BREAKS ARE 1 ORANGE and 3 YELLOW = cycle one complete
CYCLE 2: 1 orange and 2 yellow (non tank) THEN 1 yellow (tank) THEN 1 yellow 2 purple (nontank) THEN BREAKS ARE 1 ORANGE 1 YELLOW 2 PURPLE = cycle two complete
CYCLE 3: 1 orange 1 yellow 1 purple (non tank) THEN 1 purple (tank) THEN 2 purple 1 blue (non tank) THEN BREAKS ARE 1 ORANGE 1 YELLOW 1 PURPLE 1 BLUE = cycle three complete
CYCLE 4: 1 orange 1 yellow 1 purple (non tank) THEN 1 blue (tank) THEN 2 blue 1 green (non tank) THEN BREAKS ARE 1 ORANGE 1 YELLOW 1 PURPLE 1 BLUE = cycle four complete
CYCLE 5: 1 orange 1 yellow 1 purple (non tank) THEN 1 blue (tank) THEN 3 green THEN BREAKS ARE 1 ORANGE 1 YELLOW 1 PURPLE 1 BLUE = cycle 5 complete
CYCLE 6: 1 orange 1 yellow 1 purple (non tank) THEN 1 blue (tank) THEN 3 red THEN BREAKS ARE 1 ORANGE 1 YELLOW 1 PURPLE 1 BLUE = cycle 6 complete
CYCLE 7: 1 orange 1 yellow 1 purple (non tank) THEN 1 blue (tank) THEN 1 green 2 red (non tank) THEN BREAKS ARE 1 ORANGE 1 YELLOW 1 PURPLE 1 BLUE = cycle 7 complete

at this point you timewarp and kill boss = gg

CYCLE 8: (as boss is dying ) 1 orange 1 yellow 1 purple THEN 1 blue (tank) THEN 1 orange 1 yellow 1 purple (non tank) THEN BREAKS ARE 2 orange 2 yellow = cycle 8 complete

there is no cycle 9 cause i would not advise getting into 9 cycles

Now you are saying "oh I don't understand this or omg a wall of text or why are you saying orange yellow purple blue green red ( well its the color markers going from left to right, yes saying it again cause people get intimidated by comments that are long winded like this one but the achievement is long winded as well so you have to take appropriate measures to be effective!

I will say cycle 1 breaks 1 4th wall cycle 2 breaks 2 4th wall cycle 3 breaks 3 4th walls cycle 4 5 6 7 break 4 4th walls so you got 20 4th walls by the time cycle 7 is done

Credit: Bòro-Stormrage

There will be negative votes on this only because it is not "addon friendly" and has to be written down "manually" and in a world of convenience with addons this comment will get negative votes cause it is a wall of text or not addon friendly. If you want to break the 4th wall you have to have a wall of text sorry no shortcuts!

I want to add I tried this another time in a different group and it did not work out as planned. Some people didn't make it to the color markers in time. Some people just don't get it. If you are in a group like that this won't work. Maybe in future expansions where you take little to no damage from the enrage and you can solo the achievement would be feasible but that is "thinking in the future expansions" when nerfs happen like you outgear the old content. I can see this achievment being soloable someday in the future if the bosses enrage goes away like some kind of nerf but at the moment this achievement can be very tedious with people putting the wall creates/breaks on the wrong markers.