Yeah, but propelling them out of the solar system just sounds like the kind of fake-ending that ends up with the super villain coming back stronger in a decade. Have we learnt nothing from science fiction? You have to destroy your foes whilst you can.
It's definitely harder to decay the orbit into the sun directly than it is to get to escape velocity. But to play devil's advocate, there is probably a way to get them into the sun while being a similar cost to escape velocity. All you need to do is burn prograde to a super high aphelion, ride all the way out there to Pluto or whatever and then do a small retrograde burn to bring your perihelion inside the sun's photosphere. When you then get back towards the sun years later you would slam into it with a sick velocity that I think would be worth the decades-long wait.
Why is that - wouldn't you be working against solar gravity? Like you don't have to get them there quickly, just launch them in some orbit that will decay and be taken in?
Launching someone straight into the sun is very very expensive but doing a gravity assist around Jupiter or something to redirect your orbit into the sun is much cheaper.
Instructions unclear. I'm going to the moon on Delta IX.
(Edit: my dumbass just realized it's ∆V, as in velocity. I thought Delta 5 was the name of a type of chemical propellant. Though now that I think of it, it really should be. Damn, and I work for a space company too. At least I'm just in IT).
If the idea is to be rid of the person completely, we don't need to fire them into the sun. Or launch them out of the solar system. They don't even need to reach earth escape velocity.
Just launch them at the sun. Use whatever method you like. Just get them high enough that after gravity starts to overpower acceleration, there is no chance for survival. Boom! No more person. For the most part.