Man, the whole 'beast' thing with Chuuya is one of those brilliant narrative gut-punches that gets handled so differently depending on who's looking. Most of the Port Mafia rank-and-file? They don't see it as 'Chuuya-san's beast nature,' they see it as 'Chuuya-san's overwhelming power.' It's an asset, a terrifying one, but it's also his. There's this unspoken understanding that the beast and Chuuya are a package deal, and since he's their executive, that package is to be respected and feared in equal measure.
Akutagawa's reaction is probably the most clinical. He respects power above all else, so the corruption just registers as another form of strength, albeit a messy and costly one. He'd view it as a necessary weapon, not something to be 'reacted' to emotionally. The real interesting dynamic is with Dazai. His reaction is less about the beast itself and more about Chuuya's willingness to use it. That 'sheep dog' comment cuts deep because it's framed as a choice—Chuuya choosing to leash himself to the Mafia, choosing to unleash the beast for them. Dazai sees it as a tragic flaw, a vulnerability he can exploit, but also the thing that makes Chuuya fascinatingly predictable in his unpredictability. For Mori, it's pure calculus: a strategic resource with a known price. The ally who probably has the most 'normal' human reaction of horror and concern is, weirdly, Kouyou. She sees the cost, the damage it does to him, and treats it like a dangerous, chronic illness in a little brother she's trying to keep alive.