Just get your sim very happy... have him watch the comedy channel and then have another sim tell him a few jokes, he'll be dead by hysteria in no time at all. Want a fire death... forget it unless you are prepared to stack a million items in front of a fire that has no upgrades on or get a sim with no cooking skill on the cheapest over cook something while in a dazed or tense mood.. Death by drowning works quickly if the sim is exhausted before getting in the pool but apart from that, making death happen in TS4 takes too much effort. Even the cow plant spits the sim out on the first try!
I wish EA hadn't taken this route too, I like the thought that a random death might happen in previous games. Mostly they didn't, and I was happy with that, but just the knowledge that it might happen made the previous games more fun to play.
* edit: As for nerfing aliens, don't even get me started.
