Instructions
Obtain Lunamon as the starting monster at the game and then choose the "balanced" starter pack from the three packs offered on "Digimon World: Dusk." The balanced pack includes Gaomon, which you can degenerate to begin the process of evolving Pandamon.
Degenerate Gaomon into Wanyamon. Gaomon must be at least level 3 in order to degenerate to a previous evolution.
Train Wanyamon up to level 10 and evolve into Bearmon/Kumamon.
Train Bearmon/Kumamon up to level 19 with 390 beast experience and then evolve into Grizzmon.
Befriend Pandamon by DNA digivolving Chuchidarumon and Frigimon with over 6000 beast experience, 225 defense and level 31. Alternatively, make him be one of the starting Digimon in in the Pretty Pack.
Train Grizzmon up to level 36 with 8,000 beast experience and then evolve into Pandamon. You must have befriended Pandamon earlier for this to work; otherwise, Grizzmon will evolve into Monzaemon.