To beat Rufus in Final Fantasy 7 Rebirth, follow these detailed steps:

### Preparation
1. Ensure Cloud is fully healed. You can do this by accessing the menu during the cutscene and using potions or regular cures if available.

### Understanding Rufus’s Immunities and Weaknesses
2. Rufus is immune to all elemental damage, so you will only be able to use standard attacks against him. He also has resistances to poison and sleep, but these are not relevant to this fight.
3. Rufus can be staggered by hitting him when he is reloading or immediately after he attacks. This creates a window where he is more vulnerable to attacks.

### Strategy
4. **Attack Timing**:
– Focus on attacking Rufus when he is reloading his gun. This is a critical moment because he will be momentarily stunned, making him more susceptible to attacks.
– Use ATB commands like “Braver” or “Focused Thrust” after Rufus has attacked. These commands will leave him open longer than basic attacks, increasing your chances of staggering him.

5. **Dodging Attacks**:
– Be aware of Rufus’s Homing Bullets, which can be blocked to avoid taking damage. If you can’t block them, try to dodge them by moving quickly.
– Rufus also uses attacks like “Divebomb” and “Up in Smoke,” which can be dodged or blocked. Keep an eye on his animations to anticipate these attacks.

6. **Phase Change**:
– At around 50% health, Rufus will be joined by his companion Darkstar. The two are linked by a visible blue line. Breaking this line will pressure Darkstar, making it easier to stagger and defeat.

7. **Defeating Darkstar**:
– Once Darkstar is pressured, focus all your attacks on it to eliminate it quickly. This will give you a significant advantage in the fight against Rufus.
– Repeat the process of breaking the link between Rufus and Darkstar to keep Darkstar pressured and vulnerable. Once Darkstar is defeated, return your attention to Rufus.

8. **Continuing the Fight**:
– After Darkstar is defeated, continue fighting Rufus as normal. He will still use various attacks like “Divebomb” and “Up in Smoke,” so be prepared to dodge or block these.
– Continue to use ATB commands and attack Rufus when he is reloading to keep him staggered and vulnerable to attacks.

9. **Final Stages**:
– Keep applying pressure by hitting Rufus during his reload animation or immediately after he attacks. This will ensure that he remains staggered and unable to counterattack effectively.
– With consistent pressure and strategic use of ATB commands, you should be able to defeat Rufus in the final stages of the battle.