My Tier List for the Difficulty of Gym Leader in Reborn based on my experience with the game. This was pretty difficult as certain team compositions/ Pokemon can blow up any leaders with ease.. People will also naturally have different experiences based on their own playthroughs. However, I tried to take into account their overall team composition, available pokemon and resources, etc.
.Amaria is based on Reshiram Singles Route Battle
.Corey is based on Police Found Route
.Despite his suicide and not giving the player a bagde, I do count Corey
.Cal is not included
.I found Hardy and Serra really polarzing. Without Rain and or Nature Power they are brutal, but once you have those respective things they become super easy