The only reason I don't think Viv would go that route is her solution to problematic characters/issues is basically just sweep them under the rug and pretend they don't exist. Despite writing multiple shows where the characters are set in hell, she's really averse to featuring (intentionally) bad characters. Antagonists are basically only allowed to exist so the characters she likes have someone to dunk on or to milk melodrama, but once that's done, she wants nothing to do with them. Now if Adam was a soft sad boi, it'd be a different story.
IMO, it wouldn't be such a big deal on any other show. In fact, sometimes it's a problem, where the writers keep a villain around for far longer than they need to and the character loses all the gravitas they once hand and you start wishing they had died. But when your show is 1. Set in the underworld and 2. supposed to be about redemption, it is kinda weird you chose to just obliterate your first major villain instead of redeeming them. It just seems like such a no brainer, and if it were any other writer I might think they didn't do it because it seemed so obvious, but since this is Viv, I just think she has no foresight/plan that once Adam was gone she just went into her toybox to pull out another character to throw into the mix now that a spot opened up.