inanimate blob, take
Fearful the Paras. Fearful knows that when Paras evolve, the fungi on their backs take over and thus, the Parasect become mindless zombies. As such, Fearful is very hesitant about evolving and refuses to do so unless it's convinced that it will retain control of its mind and body, and to do that, it must solo Petrel in the Rocket Warehouse and stay alive throughout the Ariana battle there. It also wants to make sure that it won't be using the mushrooms on its back in any way, so it cannot use any moves that would imply them being used.* It also has to have Dry Skin as its ability, for the above reason.
Unfortunately, when Fearful evolves, it still loses control of its mind and body, and as such, must know 2 of the moves in the below list. Once it learns/relearns those moves, its moveset completely freezes. (In other words, once it learns 2 moves on the list, it can't learn or forget any other moves.) However, Fearful's spirit didn't completely disappear, and it, by the time you get to Kanto, conveys to you the only way for it to have control again: by having it solo Sabrina, who can remove the mushroom's influence, and then soloing Erika, who has the botanical skills necessary to remove the mushroom's roots while keeping perfectly intact otherwise. After these soloes are completed, Fearful regains control of its mind and body, and no longer fears the mushroom on its back. As such, Fearful's moveset is no longer frozen, meaning you can now teach it whatever you want.
Have fun!
*In case you're wondering, the list of said moves is in the hide tag below. Keep in mind that when Fearful evolves, it must learn 2 of the moves on this list ASAP.