>>31402317Excadrill is the most hilarious probably since you can just slap a Lucky Egg on it and sweep the whole game solo. Other easy to get powerhouses are: Stoutland (early STAB Tackle), Azumarill (Huge Power Rollout almost immediately), Heracross (Bug Bite move tutor), and the level 25 Braviary on White 2.
The most fun starter is Oshawott imo, it has the highest number of usable moves since it learns Ice moves for mixed attacking.
Other mons with stupid moveset potential are: Eelektross (probably has the most in the regional dex), Mienshao, Lucario, Arcanine, Flygon and Zangoose