Pokémon Diamond and Pearl/Eterna Forest

This place would probably be the hardest place in the game, if it weren't for the incredibly useful ally who decides to have you escort her to the exit. She will not only fight alongside you in every battle, she will also completely heal you after every fight, trainer and wild. So sit back, relax, and enjoy the experience points that will undoubtedly pile up after you get through.

Now, to get out of the forest, it's pretty simple. There's never more than two ways to go (besides back), with the one way takes you farther on, and the other way taking you to an item such as an Antidote ot Potion. So "fight" your way through, and at the end she will thank you for escorting her (even though she technically escorted you). You're now ready to move on!