I think what also worked about Jack is that he was intimidating actually. Like, ask yourself outside say Satan, Vox and Adam being 50/50, are any of the villains in Boss or Hazbin an actual threat?
Those three are probably the only ones that are allowed to still be actual threats even with their more laughable moments (Assuming Satan will remain consistent in future appearances). These are the only ones that at least feel like they are or can be real threats whether it be in the leaks.
But the only other ones I can think of that were actual threats that actually worked are Striker in his first appearance, John Waters in Ghostfuckers, and maybe Lute.
Then there's Valentino and Alastor who intimidated Angel Dust and Husk but either are a complete joke otherwise (Valentino) or spend their screentime trying to show off how cool they are (Alastor). Mammon also has a scene like this with Fizz but his threat pretty much diminished given Fizz just got out of the contract and has Asmodeus to protect him so Mammon becomes a comedic villain.
So really its only a small minority of villains, though there are villains I forgot to mention who are in Helluva Boss since that show has a more expansive rogues gallery and it became a soap opera so Vivzie tries to make these villains intimidating but it fails, and these are all the overarching villains in that show:
- Crimson who is hard to take seriously at all between his voice and how he got his ass beat in a later episode in a humiliating fashion while also being outsmarted by Chaz in his first appearance. We're meant to see him as this abusive father figure that overwhelms Moxxie yet he is a dumbass. This is probably going to be the template for Blitzo's Dad and Paimon later who are probably going to step up into villain roles.
- Stella whose more comedic and just a jerk who is unintentionally more sympathetic than the supposed good guy Stolas. However, we are meant to see her as this gaslighting evil woman who wants to ruin Stolas' life.
- Andre who is meant to be seen as this big brain mastermind yet is pretty pathetic and has plans that are stupidly convoluted that somehow work out. He's even stopped from killing the cast because Octavia threatened to tell Stella that Andre got humiliated.
- Vivzie somehow still tries to make Striker intimidating yet she also wants him to have funny moments in every appearance in Season 2.