I would like my non-active sims in town to be able to assassinate autonomously but I’ve had no luck. Auto is set true but I’ve never had a non-active assassinate. I’ve tried giving certain sims the “evil” trait, putting them in the mob career, having a high death push chance but nothing seems to be working.

Did you als set everything right under the careers options for assassination under city hall?
Careers-Interactions

In the FAQ you can read that The Family Career is also needed
Careers-Assassination-FAQ

You can try raising the maximum liking gate for autonomous. By default it's set to 0 so they will have to hate each other for it to happen which rarely happens outside of SP personalities. In additional unless they have unlocked the Reaper reward, they have to be on the same lot as their target for it to happen so unless you simulate community lots a lot and they are on it with non-relatives and close family members (unless you disable those settings too), it'll likely never happen.