I can count a few times when this arc has already gotten real without having even making it to Meruem and the Royals yet. And that's what I think makes this arc so great.
1. Gon and Killua face the ants for the first time in the cave. It truly showed just how weak they were.
2. Episode 85.
3. Their bouts with Kunckle and Shoot to see who was going to make it on the team. As an anime only watcher I was honestly surprised by the outcome since in most shounen the hero would somehow pull through. But to see both Gon and Killua fail + Gon losing his nen for 30 days was refreshing to see.
4. Killua vs Rammot.
5. Ants ep. (feitans finale)
6. Knov placing the entrances and exits
I agree with this post. This show has had so many ups it's amazing.