Fat Chocobo is Battle Intel Report #10 for Chadley in Final Fantasy VII Remake. He has a large amount of HP, which is why he's the ideal target for achieving 300% stagger damage and claiming that elusive trophy.
Here's how we reached the landmark.
Fat Chocobo and 300% stagger damage
Firstly, you absolutely must have Tifa in your group, since she is the only one who can increase the stagger damage percentage easily.
You also need True Strike, the technique gained from Tifa's Purple Pain weapon. This attack increases stagger by 30% on its own, so it will crucial in achieving our goal.
To stagger the Fat Chocobo, the process is quite simple: hit him hard, hit him often. The final hit of Cloud's basic attack combo when in Punisher Mode is particularly effective in adding to the stagger gauge.
As usual, max out your ATB bars — this will be very important for Tifa. Have her earn two bars, then use Unbridled Strength to evolve her unique ability (Triangle) to Level 3. Stack up two more ATB bars after this.
Once staggered, launch her three unique attacks — Rise & Fall, Omnistrike, and Whirling Uppercut (in descending order of strength). Then unleash two True Strikes with the ATB bars you've saved up.
This should increase the stagger significantly. If needs be, switch characters for more increase. Cloud can use Focused Thrust, and Aerith can use Ray of Judgement.
The Fat Chocobo is also the perfect punchbag for experimenting with team compositions, combos, and for optimizing your stagger damage. Give it a go and see, you'll also earn AP for each victory, helping level up your Materia!