There are several ways to destroy the Universe.
None seems easy for any aspiring Universe Destroyer: the Universe has taken more hits from stars exploding and galaxies colliding that you had breakfasts in your entire life, so this task may seem impossible for the faints of heart.
However, we, humans, are a resourceful little animal bent on destroying most things around us which means there are no reasons to despair if you are really committed to this goal.
Without more ado, I give you a concise but effective guide, dear Evil Lord in the making.
Spontaneous disappearance.
Not easy to achieve, but according to quantum mechanics it could happen.
The odds are very small, so you must have patience.
It is the easiest way: all you do is wait… and wait… and wait…
Annihilation with antimatter.
Equally difficult, you should use enormous amounts of energy to create antimatter, and that is not an easy matter.
For example, CERN facilities in Switzerland can produce 10 million antiprotons per minute
This may seem a lot but it would take 100 million years to produce 1 gram of antiprotons at that rate.
As the Universe has around 3 * 1055 grams, the time would be large... and that is an understatement.
NOTE: Nonetheless, when producing antimatter you create neutrinos so, in the end you would have converted the entire Universe into them but, hey, be practical.
However, this article is not about making the Universe to disappear, but to be destroyed: converting the Universe into neutrinos classify as destroying it, at least in my book.
Throwing all mass into black holes
That may be simpler: you only require mass drivers that hurl all masses in each galaxy into its black hole core.
As there are a few galaxies around and travel time to each galaxy is a tad large, it seems another long project but, in principle, feasible.
NOTE: You can see this as a failure, dear Universe Destroyer, as we still have a Universe, but full of black holes.
However, given the patience, a quality definitely needed for a mighty Universe Destroyer, you just have one singularity when all the huge black holes you have created collapse, after a few billion years, into one single huge singularity (I like that phrase: the single singularity).
Is that a Universe? I don’t think so.
For starters, I imagine space itself could collapse around this black hole (I have no idea if it would, for sure) and, finally, space itself would disappear: bingo!
That would be a tad disconcerting for me: I have always thought that the space in some way is a property of matter.
After all, how can you talk about space if there is nothing around to “have space in between”? … but I digress.
Self - replicating machines
That’s, perhaps, easier.
That would be my approach, if you ask me.
You build a machine to create antimatter AND able to replicate itself… or you build a mass driver able to throw all mass around it into the black hole at the center of the galaxy AND able to replicate itself.
Exponential growing of the machines, plus the fact (in the case of the black hole approach) that you can suck other galaxies into the HUGE black hole you would create should diminish time.
For example, if you could create self replicating mass drivers able to throw mass into the black hole at the center of a few galaxies you would create a large attractor that slowly (in the beginning) but surely, would end sucking all galaxies in the Universe into the Big Crunch black hole.
How to prevent the machines themselves from being sucked into the black hole would be another task but, hey, gimme a break.
Adrian Bowyer (left) and Vik Olliver(right) are members of the RepRap project. They seem oblivious to the consequences of their invention. The fools!!!!
*Source: *Wikipedia - RepRap Project
##Note
Those interested in the evolution of self-replicating machines could read the short story by Anatoly Dneprov that provides you with a little enlightenment.
“Crabs walk on the island” is the story of a little mechanical crab that can replicate itself
*Source: *You can read the story here
The "crab" Anatoly talks about is a small machine, powered by solar cells and its only purpose is to locate raw materials and produce a machine identical to itself, a tad like ourselves.
Once the raw materials end, the machines can only reproduce themselves by cannibalization, so machine evolution starts: they kill each other and small mistakes are made during fabrication so the "plans" to build the new machines slowly change with each generation.
Of course, being a Russian sci-fi story, it has a sad end, but it would be an instructional and useful story for a Universe Destroyer, given the fact that this particular path to evolution ends in the same humongous, very Russian, huge and solid organisms like the gigantic dinosaurs we find on Earth 60 million years ago.
Just let me explain this: if you build machines that seek raw materials with such urge that they destroy anything in their search for those materials… do not use steel fillings in your teeth, as the Russian chief engineer discovers.
My advice is this: never ever create self replicating machines to destroy the Universe if they can use planets like Earth, unless you want to miss the show.
Final Note
Another problem you could encounter, estimated Thanos's Son, is that any machine smart enough to destroy the Universe could have goals of its own.
The story you could use to enlighten yourself is the masterpiece by Philip K. Dick with the title of “Second Variety”.
*Source: *You can read this fascinating story here
Someone invents machines to destroy humans in a war between the "old" USA and the "old" Soviet Union… and not before long the machines themselves invent other robots: some of them are the second variety because they destroy the other varieties.
That would be a definitive failure for you if you want to destroy the Universe by self-replicating machines, like ourselves: these machines could NOT want to destroy it and dedicate themselves to destroy the destroyers: this means to me that there is always hope.