Celendion had a really satisfying end.
Forced into a non stop kill chain by creatures he considered bugs. And then immediately after forced to take his own life as he begs the people he called inferior just moments ago to give him an honourable death. He realises how much he took his own immortality for granted right before the end, and in response to his monologue of realisation Ash hits him with "I don't care, fucking kill yourself"
What a great way to end this guy, and a very fitting conclusion for a monster who killed so many and as the end to the first boss wave.