Like what duckbuster said, I really love Act 4. It's the perfect blend of Act 1-3's bullshit and the more serious shit of Act 5 onwards. There's still so much mystery around the trolls that haven't been fully revealed yet and it's exciting to see and learn more about them before we can finally meet them proper. It's got a lot of top-notch and iconic flashes, like [S] Jack: Ascend, [S] WV?: Rise Up, and of course [S] Descend. It's a hard act to beat, in my mind.