The Great Escape is a quest in Chapter 17, "Deliverance from Chaos" in Final Fantasy VII Remake. While Cloud Strife buys time to escape, Barret Wallace, Aerith Gainsborough, and Red XIII attempt to flee the Shinra Building.
Walkthrough[]
Hold 
when prompted to use the menu at the start of the cutscene, as a boss battle commences against the Arsenal, with Barret and Aerith as party members. All elemental 
Magic Materia are useful in this battle, but Lightning Materia provides spells that are guaranteed to hit.
The Arsenal deploys two barrier drones that shield it, and uses ranged gunfire. Barret and Aerith can both hide behind debris as cover, and this is crucial for when it charges its main attack. It will also deploy electric attacks at range, though the target reticule indicates where these will land on the ground, and thus they can be avoided. Use ranged attacks and use magic against it, and Aerith's support abilities can boost the party as they do so. Attack the right arm when it becomes vulnerable. The boss will target one character at a time, meaning as it targets one, the other can be switched to. The Arsenal can also destroy debris, though debris near the back or the pillars can be used for cover instead. Occasionally, Red XIII will use Sidewinder, staggering one of the drones, which can then be destroyed by both characters.
Once the drones are destroyed, The Arsenal's defense is gone, and its wheels are exposed though they resist damage until the boss is pressured or staggered. Avoid the boss's ranged attacks, and cripple its right arm when exposed to pressure it, then destroy the wheels. Most damage can be dealt against its main body until the wheels are exposed. Destroy one to stagger it, then lay into it with spells. After it loses half HP, the Arsenal can use Pulse Cannon, which must be avoided by hiding behind debris. Once it is reduced to 1/4 HP, it will charge Cry Havoc. Hide behind debris or a pillar, then when it charges up the next, use powerful abilities such as Barret's Maximum Fury to defeat it quickly.
Once the boss is defeated, a cutscene commences. This leads into "Flying Through the Night".
Hard mode tips[]
Using 
MP Absorption Materia on Aerith is greatly beneficial to her spellcasting ability, while Barret can be built to physical damage. Both can make good use of 
Refocus Materia, especially with Transference Module on Barret and Spectral Cogwheel on Aerith. Barrier Materia + Magnify Materia can be a good combo on Barret to protect the entire party.
Aerith should use Arcane Ward from a safe distance, allowing her to dualcast powerful spells. She can get by on using low level spells, as these still deal significant damage especially under Arcane Ward. Barret should use Lifesaver to spread the damage and protect Aerith, and focus on Maximum Fury as before. As in the original fight, switch between the two to provide different forms of damage based on what the Arsenal currently resists. When it is pressured, and during the very last phase of the fight, Aerith can use high level spells.
Defeating the Arsenal will earn Aerith the Telluric Scriptures Vol. XIII.