How do you make an evil zombie in the sims 2?

Well, first make a horrible Sim(s) in Create a Family, move them in, ect ect, then kill one of them off (or more if you prefer), then use the phone to call the Grim Reaper (the phone that it in the career rewards part, your Sim must have a high level work in the Paranormal career track which comes with University if your Sim has been to University), then tell him the Sim you want to bring back, but pay him a low price, then your Sim will come back as a zombie. Zombie Sims have low skills and low personality so they will be meaner, because you already made a horrible Sim, it will be even more meaner as a zombie.

If you don't have a high career reward or whatever so you don't have the phone to call the Grim Reaper, you can click Ctrl, shift and C, a box should appear at the top of the screen, type in:

boolprop testingcheatsenabled true

Shift click on your Sim and then click "Sim Modder", then click "career Rewards" and you will have them all. (You must have University to do this).