My mission, if I choose to accept it:
Simple! Save mankind! Save the Earth from death by overpopulation, make it WAY more relaxed, and nuke nuclear war in the bud.
The first thing I would need to do is make it so the Earth isn't the only place we could call home. My first superpower would be:
Atomic Manipulation power of Captain Atom
Currently, we only have one planet to live on. But hey, there are tons of planets out there, getting discovered all the time, that we could go to! But hey again, they're millions of lightyears away! So what can you do? Alter each planet in our solar system at a molecular level so it will sustain life. So many humans, now we have 8 more planets! Humans that like the cold? Go to Pluto, where you can enjoy the cold for 248 earth years! Or 70-80 of them, however long you make it. Or if you prefer it a little hotter, go to Mercury, and age super fast and get that super awesome tan you've always wanted! And you know, still live and stuff.
Make Earth way groovier for those of us who have a fear of interplanetary travelling:
The plant controlling power of Power Plant (Sky High)
Sure, Poison Ivy a little more popular, but she's a baddie, and well, Caitlin Freaking Snow!
This planet is too damn uptight. What it needs is pot! Everywhere! I'd make it sprout up in the White House's lawn, deserts, and gardens across the globe. Every nation would have to make a choice: spend trillions on mowing it down, only for me to make it pop back up again seconds after it gets cut, or make gazillions off of the taxes they would make on the stuff. Not sure how they would make people pay taxes to smoke a weed growing in their own back yard, but I'm sure the government would figure it out.
Because we know that humanity will still find a reason to go to war:
Engergy absorption power of Michael Korvac (The Enemy)
No more countries going nook-le-ar on each other!
There you have it, 3 random and weird superpowers that most definitely, 100% for sure, absolutely will make the world a better place. That's a presidential promise!!!