Any ways for sims to kill another sim?

Emotional deaths could be brought about in the right circumstances. You'd have to take care not to have your killer sim suffer the effects.

If you own City Living you can cook them pufferfish nigiri. Sims who eat pn that is not excellent quality die from poisoning. It has a fun animation too. There are many other ways too kill someone but they are less direct. For example you can lock sims outside when cold and then ask them to change into swimwear (they will die from freezing). Pufferfish is the most realistic though.

Lure the unsuspecting sim into a room and lock the door. For extra fun, stand outside the door saying "it puts the lotion in the basket."

"somewhsome;c-18229978" wrote:
You can also make death flower scented flower arrangements. It will age up sims, and will kill if a sim is an elder. (edit: when gifted)

One of my favorite methods, lol.

Also, if you have Jungle Adventures, you can poison sims, electrocute them, or make them combust (fire.) It takes a bit of work, because you need to find relics to make the totem. Maybe there's a cheat, or you can get one from the gallery?
Electrocution Curse:
https://i.imgur.com/mrGB2zp.png
https://i.imgur.com/fAV8vmZ.png
If you make the totem using a rare crystal, it causes death by poison. If the sim isn't cured in a few days, they will die.
https://www.carls-sims-4-guide.com/gamepacks/jungleadventure/relics.php

Yup!
A sim can use the Freeze Gun on another sim. >:)
A Bunny Rabbit can attack & kill a sim. >:)
An Evil Chicken/Roster can attack & kill a sim. >:)

Eco Lifestyle has an option to upgrade the toilet which will set your sims on fire when they use it.

"SERVERFRA;c-18230261" wrote:
Yup!
A sim can use the Freeze Gun on another sim. >:)
A Bunny Rabbit can attack & kill a sim. >:)
An Evil Chicken/Roster can attack & kill a sim. >:)

how to use the freeze gun?

A vampire with the power that gives strong emotions can cause an emotional death. I find that anger doesn't always make them mad enough to die, but death by embarrassment worked right away.