Fateful Confrontation is a quest in Chapter 2, "Covert Ops", of "Episode INTERmission" in Final Fantasy VII Remake Intergrade. After Scarlet sends Yuffie Kisaragi and Sonon Kusakabe to fight various weapons in the testing facility on B20 of the Shinra Building, she invites them to take the elevator up to another floor, where a challenge awaits them on B12, where the Heavy Weapons Platform Testing is located.
Walkthrough[]
After taking the elevator to B12 - Advanced Weaponry: Research, a much-needed bench is available. Use it and take the opportunity to prepare for the boss battle ahead. The main boss is weak to 
Lightning, while one component is weak to 
Fire; however, the main boss has resistance to fire, meaning 
Lightning Materia and 
Elemental Materia is best on Yuffie's shuriken. Having access to healing on both party members is ideal, and pairing Healing Materia with Magnify Materia on one or both is helpful.
Down the corridor, a boss battle begins against Scarlet in her mech suit, the Crimson Mare. The Crimson Mare can deal heavy damage with bullets, which should be guarded against. The suit is also capable of charging through Yuffie and Sonon, which should be dodged. Scarlet also summons Sentry Rays and Sentry Launchers, which are small and can be dealt with quickly using Throw, but deal enough damage that they are high-priority targets.
While the Crimson Mare is highly durable, Scarlet has less HP. Targeting Scarlet by using Throw and Retrieve to attack her is ideal, as once her HP drops, the Crimson Mare becomes pressured and is vulnerable to damage. Synergized Art of War and a charged Banishment are effective against Scarlet and her mech suit.
When the Crimson Mare's HP falls to 2/3, a short cutscene commences and the boss returns with two mako cannons that deal heavy damage when fired, making it important to heal often. Much like Scarlet, using Throw and Retrieve to attack and destroy cannons can pressure it, rendering it vulnerable. Depleting the cannons and Scarlet's HP can easily stagger the boss, at which point, limit breaks, or simply more Synergized Art of War, should be used. Using Synergized Windstorm on a staggered foe also raises the target's stagger bonus damage.
After the boss drops to 1/3 HP, it enters its final phase, where it uses a claymore and shield. The claymore can deal sweeping melee damage in this form, but both it and the shield are weak points. Cripple Scarlet first, then destroy the claymore and shield, rendering it vulnerable to damage, and easy to destroy.
When the boss is defeated, a cutscene commences, leading to the next quest, "A New Threat".
Hard mode tips[]
Most of the same strategies apply as before, though it is important to keep up 
Regen and use Brumal Form to dodge the harder-hitting attacks. Defeating Scarlet in hard mode will grant 10 SP books to both Yuffie and Sonon.