Well i am interested how kaido uses methods in torturing people.
1. Jack tortured inu or neko using chain crossbow.
2. Udon prison is similar to gate of hell where they are punished for against and crush their moral.
3. Kill by boiling - oden s death is probably horrible one.
It reminds me of seven deadly sins the people who goes to hell are punished with their crimes.
Kaido in hindu mythology can be related king yama god of death.
King as hell gatekeeper. I was interested he choose king impel down guard .
I just did this reaearch in my spare time. Kaido as god of death shares same qualities.