The fastest way to kill a sim

Update, they got out of the wall!!! They gotta go!

Are they household Sims?
Or are they duplicates from another household who are guests at your house?

There's lots of ways to do this, but it depends on what packs you have and/or how open to cheating you are.
Seasons you can gift them Death-Flower-scented flower arrangements, which will age them up one life stage each time, killing them if given one when they're elders.
Could be fast if you cheated your Flower Arranging skill up and gave yourself death flowers to do this.

With seasons, you can also try to kill them via temperature.
Cold's easy, just use the weather machine to make it a blizzard, and trap them outside and/or in a pool surrounded by fences.

If they're locked in a wall, death by starvation probably takes around 3 Sim days.

Just make sure when the bite it to release their spirits, or else you'll have duplicate ghosts running around.
I'd say to just split the households and delete them, though.
Easier, and no ghosts.

ROFL...too funny.

You need to delete them from the household manager in neighborhood view after moving them out to get them to stop showing up in the world. That should be all it takes.

As far as the fastest way to kill them, fastest would be using a mod like MCCC to instantly kill them with the death-method of your choice.

Without mods, In winter it's super fast killing a sim if you take them to an outdoor pool when it is cold and force them to swim. Make sure they don't have (m)any positive moodlets when you send them into the water and it is nearly instantaneous.

In summer, you could use heat to kill them by making them spontaneously combust while hot, by having them drink coffee or some such. I think you need to get them on fire twice for it to kill them though.

Death by hilarity is also really easy to obtain if you have a house where you can stack up a lot of happiness moodlets. Just get them stacked up and then take them to an area with +playful decor and make them do some playful interactions. Get them to Hilarity with a total of +15 total Happy + Playful moodlets. For me, this one is the easiest death method. I have to use a mod to prevent playful death or my sims die from playful all the time when I am not watching them.

I like to make the offending sim a vampire and then make them wait out in the sun. Nice animations :)

In order to make a vampire

traits.equip_trait trait_OccultVampire

If it is early spring for you, chuck them into the pool and let them swim around abit. Fastest way to die I have ever seen. Poor Liberty Lee, still has nightmares from her death experience.

Hmm, I don't have the vampire one so I will try the pool. I considered making them deathly ill but that cheat isn't working for me.

Pufferfish nigiri if you have city living. If they eat the dish while in a bad mood or if it's just made poorly they'll definitely kick the bucket.

Fastest method I know of: MCCC.

First of all, talking about killing Sims is just like talking about your favorite ice cream - totally normal.

Now back to the topic... Death of starvation is too long, you need more than 2 days, depending on their hunger bar. If you have Season, you can try swimming in freezing temperature. Or you can serve bad nigiri sushi. Death by laughter needs too much set up, IMO.

It used to be so much easier when you could just take away the pool ladder, lock them in with a stove, make them repair something...