The way Hunter's eyes were purple/pink again in this scene
Yea Belos' death was anticlimactic but honestly that was kind of the point I think.
He was a pathetic old man throwing his power around to hurt others, holding onto his own delusions of being a hero, believing he was better than everyone and everything. He doesn't deserve to have a climactic death, to go out with a bang.
He was nothing. Just a melting falling-apart pile of goop and bones desperately clinging onto the dredges of his own self-importance, still trying to act like he was somehow better than anyone else when he's nothing, and everybody knows it. He's not fooling anyone anymore. He's nothing and everyone knows it.