Final Fantasy 7 Remake Leviathan is a powerful summon the player can use to their own advantage in combat. Unfortunately, like most summons of this caliber, they'll need to prove themselves worthy first and defeat it.
Here's some tips on taking down Leviathan.
Final Fantasy 7 Remake Leviathan
To unlock Leviathan, you'll need to complete Chadley's reports 1-14 and unlock Shiva and Fat Chocobo. Available characters for this fight are Cloud, Barret, and Tifa.
Leviathan is immune to poison, silence, sleep, slow, stop, and berserk abilities. It has greater resistance to fire, fixed and proportional damage. Its primary weakness is lightning magic.
When actually battling Leviathan, the main things you'll want to keep in mind are to stick close to it and to keep healing in the forefront of your mind. This creature has a lot of ranged abilities with a wide area of effect so it's possible for all your team to be hit at once. Magnify might be something to consider here.
Leviathan's abilities are Briny Bellow, Briny Barrage, Gyre Spume, Tail Whip, Aquatic Focus, Tidal Roar, Spinning Dive, and Tidal Wave. These all might sound equally challenging, but the real trifecta you want to keep an eye on are Gyre Spume, Tidal Roar, and Tidal Wave.
Gyre Spume is an anomaly among its abilities as it is the only one that makes close combat more dangerous. Leviathan will draw the team in and then deal damage around itself. Retreat swiftly to avoid damage.
Tidal Roar causes Leviathan to fly into the air—yes, it flies—and cause water to spout on the battlefield. This is where Barret has the most value as he's the only one who can reach. Don't try to aim and fire through the water spouts, however, as they'll block any damage you throw at them.
Tidal Wave is its ultimate ability. Fortunately, it takes a bit of time to charge up so you'll have time to prepare. Some players have reported success in staggering Leviathan as its charging. You'll want to do everything you can to keep yourself alive once it hits, however, as this can cause a team wipe in seconds. Heal and brace yourself.