At the table, be it physical or virtual, other players aren't necessarily happy about having an actively evil character in the group.
Really it just depends on how the evil is portrayed and its scope.
Evil is more about selfishness than cruelty.
Like, people LOVE Astarion (To the point of excess) and he's an
actively evil character. His entire concern is purely his own wellbeing and power.
He's not comically cruel, he will go along with a goody-two-shoes party and even help save Tieflings. Since he's evil, not stupid. Tagging along with a group of powerful individuals serves his own purpose, which is to deal with the mortal peril that is the tadpole in his brain.
This all goes to highlight the major issue with how evil routes are written vs actually decently written evil characters and companions.
What players get is "Murderhobo Supreme" the route, where all choices are about being the biggest jerk in existence and causing suffering for no reason other than "Because you can". Meanwhile actually decently written evil characters are relatable, reasonable and smart enough to go along with things they don't necessarily agree with in order to fulfil their long term goals (Another example is Gortash. He's evil af. But he played nice to get to his standing within Baldur's Gate for the power it gives him)
This divide is why evil routes often feel undercooked and get complained about. As they almost always boil down to just being cruel for no reason. When you see plenty of well written evil characters who aren't that, whom embody the more nuanced aspects of an evil character.
A proper evil route can have a lot of parallels with a good route, it can even have morally grey aspects that are hard to discern from good routes.
For example, a player can find themselves obtaining a powerful artefact. They then are given a choice. They can use the powerful artefact to gain power (Evil) but this power could be used immediately to help a lot of people (Good) with maybe consequences down the line (It might be cursed, it could have a price for the power, it can you actively look for more artefacts to boost your power etc all things that could be evil in nature). Or they can give the powerful artefact to a group of people who would seal it away (Good) at the cost of not being able to help those people who are in immediate peril (Evil) but there won't be any nasty consequences from utilising said artefact (Leading to an overall good outcome).
It's one of the annoying aspects of writing in regards to becoming a Vampire or Lich. They are always unanimously written as evil... But like, what if someone became one of these things to use the power exclusively to help others?
Like, Alucard from Castlevania is a vampire and the son of Dracula, but he isn't evil and instead uses his vampiric gifts to fight the forces of evil (Including his father, Dracula himself). Heck, even Dracula wasn't completely evil in Castlevania, he preserved human knowledge and even shared it with a woman who was interested (But he went full evil as a crash out to her being executed because people are idiots).
You also have Angel from Buffy the Vampire Slayer who, due to the curse giving him his humanity back, actively helped Buffy to deal with the monsters and threats (And eventually got his own spin-off show where he did it more independently)
Heck, the entirety of DOS2 is you being morally grey. You perform evil acts (Devouring people's souls) but only as a means to ultimately save the world. You become a hero, despite the fact that you've been committing atrocities through most of the game (The entire game if you've been min-maxing experience gains on the island)
