sure, go SD a freighter in a system's star and see what happens

Pump some iron in to that sucker. insta kill :)

^^ im not joking btw Iron is the way to go. Delivery is the problem.

I am quite certain that a single iron atom would have no effect on the processes of a star. Setting aside that any given star at stage in its life is bound to have a very large number of all types of elements either through its normal fusion process (while most of the fusion will be of the hydrogen and helium variety for a normal star for most its life over time randomness will result in the fusion of larger and more exotic elements, especially iron) or from leftovers of the previous stars that provided the mass to form the star. Our sun, for instance, is 0.16% iron.

All the heavier elements that make up things like planets (metals, gases, and even up to uranium and plutonium) are the product from past stellar fusion processes. Large and/or hot stars can continue fusion all the way up to silicon and at that point iron will make up a surprising amount of the star's mass.

There's no element/molecule that we know of that could be introduced in small amounts to a star to disrupt its process in any appreciable way. Unless we want to talk about exotic forms of matter, like strangelets or something, the only way destroying a star through the introduction of outside material will necessitate just a very, very large amount something (just about anything would probably do). We're talking about a lot though. I have no idea how much or how to calculate how much iron it would take to disrupt the sun's fusion process but if it were even only 1% of the sun's mass you're talking about a lot of iron.

Again, I did some math (probably badly) and what I calculated was that a block of iron equal to 1% of our sun's mass would weigh 22 trillion trillion short tons and would be 18.5 billion trillion cubed miles in volume. That's a cube of iron 26.45 million miles on each side. If anybody plans on trying this do tell so that I can invest in mining lasers now.

EDIT: I think the reason that the hypothetical block of iron is so much larger than the sun itself is because I did not (and could not even try) to account for how the block would collapse under its own gravity and reach a much higher density (and thus much smaller volume) than normal cast iron. The actual ball (you couldn't keep it in cube form) would likely be much smaller but the above still illustrates, I hope, the gargantuan amount of material we're talking about.

You could use the Hand of Omega to turn a target star into a new Eye of Harmony. No more star plus you can power a TARDIS.

@davis you're right normally the start off iron production ours the start of the end. When the weight becomes to great it can collapse. However the iron ours only produced at the end when other reactions are no longer ppossible.. Introduction of iron won't change this. Guess we will have to use the arse of jamyl sarum, bet it's big enough.

Didnt Tolian Soran from ST Generations (the movie) do something similar?
Heck, mayby even Guinan (Whoopie Goldberg) knows! :)

Hmmm, if I remember correctly, Soran launched a missle towards the sun (of the planet he was on) which caused the sun to explode, which changed the course of the NEXUS string, which swallowed up Soran and sent him to blissfull heaven, but the unfortunate affect of that was the total destruction of an inhabited planet and the survivors of the crash landed Enterprise.....

of course, it was all fixed by going back in time :)

SCIENCE.

I know! Like how you are not able make one single intelligent post despite we are living in a age, surrounded by science and encouraged to think.

Seriously though. GTFO to whatever you played before you scrub.

So, maybe this is being looked at the wrong way.

What if you took a large massed ship, like a battleship, in warp, warped towards the sun, and then turned off the warp bubble generator while the ship was still going at 3 AU per second, dumping the ship back into normal space at hypervelocity. Would that create a black hole, convert into ultra hard radiation, turn the mass of the ship and anything in front of that mass into a relativistic smear?

Alright, more ideas:

Eve clearly has large scale antigravity technology, what if you strapped a giant antigravity generator to a ship, flew it into the sun, and turned it on, thus locally negating the effect of gravity on the stellar body? At the very least all the energy and matter contained within that nullified area would explode outwards, if the ship could survive getting far enough into the star, it could completely destabilize it. You could use a warp drive to get this into the centre of the star.

Could also use a ship with a warp drive that creates a very large warp field bubble to fly into the centre of the sun, and then warp off again, taking the core of the sun with them when they reactivate the warp bubble. Whole center mass of the sun collapses on that empty point, destroying the star.

Could also use the warp drive to deliver a large mass of a superheavy element, like plutonium, into the core of the star, destabilizing the fusion reaction (this might take a while)

Could also arrange antigravity field generators around an area above the surface of the star to create a giant stellar flamethrower aimed at whatever you wanted gone.

Could also use stargates with warp drives to systematically deconstruct a star for stellar engineering, by peeling away at it layer by layer.

This is just off the top of my head.