Power
You can't raise the dead, but you can tell people why they died. Not the same people who died, of course. You can tell other people, like the FBI, why they died. And then the FBI can track down whoever's responsible and slap them with the appropriate punishment. Go team.
If you're a clinical or consulting toxicologist, you're much more involved in identifying toxins and harmful chemicals than you are in curing the nasty infections, viruses, and cancers that result. In the end, however, you're still helping people and the environment—so there's a certain level of power in that. The first step to solving a problem is figuring out what's causing it, right?
You're still answering to someone, though—and you're still on the hook for doing all that paperwork. Why? Because either your boss, your biochemical pharmaceutical company's HR department, or federal regulations say so.
Even if you're the one in charge, you'll have to answer to somebody—the requests of the company employing your lab to test their products, federal law, and your own sense of moral responsibility. Okay, that last one's not a person, but you'll still have to answer to it. Like, all the time.
There's a little power in being a toxicologist, but not the kind of taking-over-the-world power that some people so desire.