How to get overpowered quickly in Persona 4 Golden.

Step 1: Get the persona Slime.
- Slime can be found on basically every floor of the first dungeon.

Step 2: Level up Slime to level 7.
- Slime learns the skill Resist Physical at level 7.

Step 3: Farm until you find a Magician arcana card.
- The Magician arcana card randomly upgrades a skill on your currently equipped persona.

Step 4: Continuing farming until Resist Physical gets upgraded into Null Physical.
- Getting Null Physical easily allows you to sweep most of the early game. (I had fused my slime to a Senri and got the Null Physical then)

Step 5: Profit.

Congrats! You can now register slime (or whatever persona you got null physical on) into the Compendium and get infinite slimes to fuse into whatever you want (use a fusion calculator to get Null Physical on whatever persona you want).