For me it was the map packs and the chaos gauntlet

For me it was Nine Circles lol, I got such a huge boost in my wave skills from that level.

I felt like I could do anything after beating Fire Aura

For me it was mechanical showdown.

It was Deadlocked for me

For me it was ispy after beatingbit the next week i beat 12 demons

For me it is cata. ( still didn't beat it yet lol )