How to Fast Farm Bonding Points in Persona 5 Strikers

For end game user who playing it on Merciless's difficulty.
This can make you fast farming to unlock Eternal Bond's Achievement.
Defeat the Dire Shadow in Sendai Jail repeatedly.

How to fast defeating Snake King.
Best team: Joker, Yusuke, Ann, Sophia.
Maximize Magic stat for both Ann and Sophia, Luck and Power stats for Yusuke.
Best skill for Joker's Persona: Heat Riser, Debilitate, Blazing Hell, Ice Age (Optional)

From the start encounter, try to maximize the potential of Attack, Speed, and Defense Master Passive skill to quick Heat Riser for Joker. Me using Chu Chulain, in this case.
Debilitate skill to Snake King. Then, Try to freeze it with Ice Age (Optional). and then Heat riser for all characters.
Spamming skill for each character until low SP and baton pass if needed.

You can defeat this Dire Shadow about 3-4 minutes for each encounter.
For me it takes about 9 hours from bonding level 66 until 99.