In comic books, time travel is almost as common as superpowers. At some point or another, most characters have experienced some sort of time travel. In the DC Universe, Barry Allen had developed the Cosmic Treadmill and Doctor Doom invented his Time Platform. Both have been used and abused by others besides the actual inventors.
In the case of Doctor Doom or any villain that managed to get a hold of a time travel device, you would think it would give them limitless possibilities to rule the world. The easy idea is they could travel back in time and kill their enemies as infants or use their knowledge of the present to lay out intricate plans or investments.
For the most part, there is an accepted belief in comic books that you can't actually travel within your timeline (especially in Marvel Comics). Traveling back in time creates an alternate reality and so any attempts to change the present will result in failure in the person's actual timeline.
There is another solution in using time travel to come up with a way to rule the present.== TEASER ==
In the recent The Iron Age: Alpha, a forgettable Iron Man villain did manage to gain access to a version of Doctor Doom's Time Platform. Determined to get revenge against Tony Stark and Iron Man, this villain didn't go into the past and try to replace the baby formula in l'il Tony Stark's bottle. Instead he went into the future. He went there and simply made observations.
You don't have to be a genius to go into the future and obtain the schematics on some doomsday device. Venturing forward could have similar time travel problems involving alternate realities but if the right piece of future technology could be obtained, it would make life a lot easier. And that's what this villain did.
It's not just villains that could gain from this. We know the story of Cable and how he was taken far off into the future so he could be cured of the techno-organic virus. When he first appeared in the pages of The New Mutants and the original X-Force series, he had some crazy looking weaponry along with the technology to teleport (or bodyslide).
For the ambitious villain, even the most powerful futuristic gadget might not be enough. There'll always be a Reed Richards or Mister Terrific that could probably come up with a solution to defeat the technology. If a villain is after financial gain, they could journey a few years or decades and pick up whatever the current technological craze is. Imagine if someone in the 70s came up with the plans and ability to manufacture an iPod or iPad? Even if there were some restraints that preventing a traveler from carrying any objects back, just coming up with the idea and being able to figure out enough to have the future tech built would be enough to set them up for life.
Going into the future and just making observations might seem like a boring plan but it's one that could prevent the villain from getting into a superhero battle and facing jail time. It doesn't even have to be a piece of technology that they observe (and steal). They could even take the idea from a blockbuster movie or novel and pass it along as their own. We know fighting isn't always the solution and you would think that eventually the villains would discover the same option.
If a villain is willing to steal in the present, why wouldn't they want to steal from the future. This could be an easy solution for them and free them from being on the receiving end of super-powered punches. The only problem for the villain is finding or getting someone to lend them a time machine.