While I playing Pokemon X in the earlier moments, I came across this character that won't let me enter because I wasn't a champion yet. Now that I have defeated the Pokemon Leauge Champion I wish to find that character, but the problem is that I don't remember where he is.
There are two areas that are not accessible when you are not champion. These are Terminus Cave, which holds legendary Pokemon, #718 Zygarde, and Pokemon Village, where #150 Mewtwo. To get to Mewtwo's Unknown Dungeon, you will need to have Surf. These two Pokemon are level 70. If it's not any of the two, then it might be the Lost Hotel, where a man also blocks you from passing, but you don't need to be champion for this, you only need to learn the roller skate tricks.