Build a fusion power plant and put money into fuel production for it.

First off, invest and diversify it in companies and startups also focused on positive change, like those creating technology for lowering the cost of food and necessities and improving lives of people with disabilities. Stuff that improves our everyday lives and creates real value in the world. Solving all the world's problems is not really something that one person can reasonably do on their own effectively, so it needs to be allocated to other groups of people where it can make a proper difference. Build housing and invest in education globally with the proceeds, helping those in need to get back on their feet. Investing it intelligently means you'll never run out of cash, and even have more year-over-year to improve the lives of more and more people. If there are a lot fewer people struggling in the world, those people can then dedicate time to solving world problems and improving lives and continue the cycle.

As you acquire more money you can provide more services to more people, make more positive investments and help and improve the lives of more people.

Shit, I think I just described capitalism. Whoops, nevermind. Sorry I know that sort of thing is frowned upon here. I think the best thing to do would be to give every person on earth $12 one-time. Well, minus the costs and logistics involved in doing that, so every person on earth can get $8 after expenses. That should do it.

Buy as much land a possible and build houses for homeless people to rent at an extremely low cost. They would need to either have a job or be actively looking for one (with proof since trying to get one shows they might actually be trying to better their life, in my eyes at least), pay for their own food, and maybe a $10 monthly rent.

The lease would be on a yearly basis and if they find a better place they can afford before the lease is up, they would be allowed to leave without any sort of early lease termination fees. There would probably be a month long period where the person(s) could move back in just in case the new place doesn't work out and they have to move out. During the grace period, nobody can move in.

I would, with the hypothetical money, pay for their utility bills and try to keep up on repairs/maintenance so long as they don't abuse it by doing something like constantly keeping the water on 24/7, using as much electricity as they can physically can, or purposefully breaking and wrecking the place.

Also, I would let them know that they would be responsible if they get their internet access cut off because they were too busy pirating. Even though I personally support piracy, I wouldn't want to be in trouble for piracy that I wasn't directly involved in.