But, but.. poor M21 was forced to shut up.

Yeah we can count that among good moments.
Among not so good: The way power ups are set up -I can't complain much as that modus operandi was established since the early arcs -originating from the single source. But I wished that had better dialogues and flow at least.
Crombell arrived -the only person who has been constantly successful even in most disastrous situation. And not even on radar of Frankenstein despite all his intelligence. No one question Muzaka what he is up to and why he is taking Garda to Crombell giving him a second test subject.