How do you play evil sims?

I have the same issue. I tried playing with an evil sim a while ago but he ended up insulting his wife and kids all of the time and making the whole house miserable lol. I actually got offended on behalf of the child he was yelling at, maybe it isn’t the gameplay for me? :D

Evil trait itself doesn't do much. You get the evil laugh animation and some moodlets. If you want your sim to be truly evil, you have to be the mastermind behind their actions. You could have your sim hate for a certain age group for example, always act mean to those sims and maybe start a hate club.

To your question how I play my evil sims. One of my evil sims is Juno Black the daughter of a feared criminal Rita Black who is now a ghost. Juno abandoned her childhood home in Oasis Springs and moved to San Myshuno business district. She took the family "butler" (played sim living with them) with her but he passed away recently. I plan to get her a real butler now. Juno is the leader of a gang called Oasis Mafia and they gather to play don't wake llama in one of my shadier community lot. Recently Juno kidnapped a child of my other family and held him as a hostage for a while. I intend to write a story of it but kind of missing inspiration. I wrote the first part but it's difficult for me to get in the mindset of an evil sim.

I have no idea, I played the criminal career with an evil sim so most fun I had was from that, I walked around and stole money and tried to create a gang.

@Thenyoukissme Glad I'm not alone in this. Maybe it might not be for me either. ? He can't even get a girlfriend like this. Do you also have the mod?

@Musteni It's probably the Have More Personality, Please mod then because it's definitely the evil trait that makes my sim like this. None of my other sims are like this, except for the two who are evil.

I never play evil sims. I don't find the traits fun at all.

Somehow evil = really rude in the sims. They are so obvious. I would love a trait where sims can have more calculating, psychopathic behaviour. That is evil to me. Although I'm not sure how well that would fit into a T rated game.

@ParmaViolet87 Exactly. That's more like what I had in mind. I wanted to create surface-level charmers who are evil underneath the facade, not sims who keep beating up others all the time. :D

That's funny that's mostly how I play most my evil sims - as a charming psychopath. I do control them though and I don't use mods. Usually I get them the friend of the world aspiration so they can start off with a great relationship with anyone just by greeting them (along with other aspirations). Usually they are mean in private.. and it's usually tailored to who I want them to be mean too.
Maybe they tweaked them to be meaner? I haven't seen that and I really hope not. It would break the way I play them. The reputation thing though usually gets bad but I often try to keep it pretty neutral because they are evil/mean to some folks and not to others. Also depending on how I use clubs it can add another layer to how people respond to them. I don't usually put them in an infamous group unless I just want them to be hated. You can also put them in a famous group to get an initial boost of likability.
I think you just have to know how to play with the game and what traits and other options to use to make the play more satisfying to you.
I have played downright mean/evil sims and going down the mischief path with careers and aspirations makes it pretty fun.. it's just not how I see real evil. That's usually how I see stupid/mean.

I have no mods and a family of two evil sims with a good child (trait rolled at random). I thought it would be hell for both parents and kid but they are getting along mostly just fine. Sometimes child receives sad moodlets from "good vs evil" but nothing dramatic. And this upsets me a lot. Also autonomously they are usually pretty neutral with others jumping from insults to gossiping and jokes.

I also would like to hear others' ideas about criminal activities for evil sims. I have a "gang" club for playing cards and being mean to others. Also my sim can pick-pocket from career abilities. The last thing I'm yet to try is raising sim handiness to break into someone's safe from Get Famous. But that's pretty much all I can think about and nothing of it (besides bank robbery) stands as super criminal/evil to me. Any other ideas for criminal activities our evil sims can participate in? And how to make them more evil?

I have a few evil Vampires and Sirens, but it's like @musteni said - evil laught and a few moodlets - that's it. Unfortunately. I never saw them get into a fight on their own, for example. I'm always the one who has to push 'em :(. Even if they're enemies, they start a freindly chat with eachother.
The fact that Sirens can't drown Sims and Vampires can't suck Sims to death doesn't make it any better. And since I don't play with mods, it just happens in my head.

I enjoy playing with my evil warlock who uses his magic to mess up other Sims' lives.
I don't make my evil Sims normally be openly mean. I think they're more intelligent than that. A lot of my evil Sims act friendly towards Sims, but they secretly plan ruining their lives behind their backs. >:)