Verified answer

The International Space Station weighs 335 tons and travels at 17,200 mph. Its momentum generates 54 million hp (40.3 gigawatts) that keeps it in orbit, otherwise it would fly off to space. It has no engine, it's powered by gravity.

The largest nuclear reactors produce only 1.5 gigawatts and the largest turbines of hydroelectric plants 0.7 gigawatt each.

Well, the nuclear power plants in ocean going ships working to overcome water drag are certainly the most sustainable and fairly powerful. I would imagine the diesel engines in deep draft super tankers have got to be among the most powerful of that type. This site http://people.bath.ac.uk/ccsshb/12cyl/ lays claim to the title for their engine for large container ships.