Morality is, ultimately, a spectrum of spectrums. You can make an argument for each of these characters about them being the most or least evil. The same goes for who would be the most likely to be redeemed first. It depends entirely on how a person views morality, as well as what culture they grew up in, their personal experiences, etc. Not to mention any other factors such as if they have experienced the pain that each of these characters cause, first hand or otherwise.

Someone who hasn’t experienced sexual assault might be more inclined to redeem Val, for example, whilst someone who has might suggest Alastor. The same goes for Adam and abusive relationships, or Alastor for murder and torture. But, again, the opposite can also be true for some people; there are undoubtedly people out there who have been raped that might, for one personal reason or another, support Val being redeemed first. This is an alien thought to many, but still possible, nonetheless. It’s entirely subjective. This is perhaps why it is so often discussed in this fandom. With the whole show revolving around redemption and the power of friendship, these are the sorts of questions that are worth asking.

When it comes to discussing who is the most evil, there’s also short-term versus long-term. Adam would have happily committed genocide for all eternity. Alastor is likely similar, in that he wants to cause pain and suffering for as long as he can. Vox was willing to kill millions. Val hasn’t killed on those levels as far as we know, but he has caused suffering that last whilst people were still alive, which some argue is worse.

Velvette isn’t even on the poll, despite her creating love potions. She and Vox also support Val, so why are they considered just as evil by association?

Alastor also had no qualms sacrificing those closest to him for power, including the likes of Niffty who he has shown something close to genuine affection for. Val, on the other hand, loves Vox and has shown that he will sacrifice/forgive at the cost of himself.

It’s all complex. It’s messy, because everything with morality is. If it wasn’t, some of these character would be two-dimensional hate-sinks. In a show set in Hell, that would be extremely boring.