Crisis Core was arguably the first active-time action game in the Final Fantasy franchise. In many ways, it set the tone for Final Fantasy VII Remake's system. This has the effect of making the combat tough, even in the early game. One of the first boss fights you'll encounter sees you fight two massive monsters simultaneously.
Best strategy for beating Vajradhara Tai and Wu in Crisis Core
You'll encounter the monsters Tai and Wu near the first chapter's end. They have hugely powerful physical attacks and can take a lot of punishment before they go down. To defeat them, you'll need to take them down one at a time. They don't have any good ranged skills, but you'll need to pick your moments carefully to wade in and deal damage.
Since there are two foes to worry about, the easy way to handle this bout is to keep your distance and lob magic at them. Both Tai and Wu take more damage from magic than they do from physical attacks. If you happen to get an unlimited MP buff from the DMW, just play from a distance and bombard a single foe. Otherwise, try to dodge past their attacks to get behind them. Pick one of the two early and try to eliminate it fast. This fight becomes trivial once you're only up against one of them.
Tai and Wu introduce special abilities to the game. They have an unavoidable attack called Twin Tomahawk that will deal substantial damage. A large purple countdown will appear on the screen before they use this attack. Abuse your strongest Materia and try to deal as much damage as possible to reduce or negate the effectiveness of this attack.
Just keep your distance, focus your attacks on one target, dodge whenever they raise their hand, and use magic liberally to take these foes down. Once you've defeated them, they'll both drop a potion to keep you going.