This is a list that is going to be listing the enemies in the first Palace dungeon of Persona 5 and what their weaknesses are. If this helps you out please feel free to share it with other people too. Also, make sure to check out the list of enemy weaknesses for the second palace in Persona 5 here.
Name: Pixie
Description: Flying fairy.
Weakness: Gun, Bufu, Mudo
Name: Agathion
Description: Ghost flying around inside of a pot.
Weakness: Garu
Name: Bicorn
Description: Horse demon with two horns sticking out of it’s head.
Weakness: Zio
Name: Succubus
Description: Floating female demon dressed in black with wings.
Weakness: Gun attacks
Name: Berith
Description: Knight in armor riding on a red horse.
Weakness: Bufu
Name: Jack-O-Lantern
Description: Floating pumpkin head monster carrying a lantern.
Weakness: Bufu, Garu, Gun
Name: Andras
Description: Bird man hybird type of enemy.
Weakness: Agi, Gun
Name: Silky
Description: Floating ghost woman enemy.
Weakness: Agi, Zio
If this helped you check out the list of enemy weaknesses for the second palace of Persona 5. Link: Persona 5 Second Palace List of Enemy Weaknesses