I always forget that the easiest way to beat the game is to get one high-power starter and just powerlevel that poop.
I always end the game with a nice team of 4-5, all 5 levels under the elite 4, and then I have to grind it.
Except for in the case of Black and White - it was actually perfectly balanced for a team of 6 and where they would be at that point <3