I don't see why restraining him would take anything more than a typical prison inmate? Maybe a somewhat reinforced cell? Invulnerable and immortal makes no difference, since you don't want to hurt or kill your inmates. The only important super ability he has is that he's a bit strong. So long as your cell would withstand a smart inmate with a crowbar and a winch, then you're good.
But first, you have to capture and restrain him. Assuming he's "invulnerable" to everything, so tasers and gasses won't work, some kind of entrapment would work - a pit trap, for example.
The encasement that others have suggested (mortar, lava, etc) should be safe since he can't accidentally be harmed. By the same measure, you could just enclose him ny driving at him with a truck.
Or what about just playing golf with him and a bunch of RPGs? Consider, you have a pit trap in a golf course. You've lured him to the golf course. Your goal is to knock him into the pit trap by shooting him with high explosives.
There's one guy with essentially zero anti-capture super powers other than "push/punch door", and he can't push a door with 9 tonnes of force since unless he has something to brace against. Exactly how far does he expect to get?
So let's flip the question around. So, we're That Guy. We can't be hurt or killed, and we're pretty strong, but we can be captured, and we're susceptible to losing our mind around people. We need to kill as many people as possible, preferably All The People.
Bombs... just won't kill enough. Going out into crowds, we won't be able to kill nearly as many and will risk capture.
And we need to kill them FAST. A few years, tops. The more time we take, the more likely they are to capture us.
So, what other options are there?
- We can leap onto air liners and plough them into buildings and walk away and grab more air liners and rinse and repeat, but after the first few all planes will be grounded and we'll just be shot down on takeoff. We'd kill hundreds, maybe thousands if we're lucky. We need to be thinking at least in the hundreds of thousands.
- Ocean liners. We could probably sink and destroy a few without being discovered before people stopped using them. But say we hit the top ten biggest ones in one fell sweep, in the first day. About five thousand per ship, assuming they're full. That's fifty thousand people, which is a decent number. Now we just need to equal or top that kill rate every hour for the next twenty years or so... OK, this isn't going to work.
- What if we destroy all nuclear plants? Most are built to survive a direct impact from an airplane, but possibly not a fully loaded Airbus A380. The reason to do this is to just make much of the planet unlivable, reducing our target area. Except... we'd need to destroy an insane number of them before we'd make any significant dent in the livable surface area, and I'm unsure there even are that many (anyone want to do the math?) Plus, after the first few, the rest would be temporarily decommissioned or protected against the plane attack method, so we'd need other approaches.
- OK, so it's all-out thermonuclear war, or nothing. But how do we start thermonuclear war? All the systems are guarded. Even if we broke into a nuclear depot, how would we fire the missiles? How do we figure out all the interlocks and safety protocols and authentication requirements? The only real way is to get into the design team.
- OK, bioweapons, then. The only real way there, again, is to get into a bioweapons research team.
There is one final option, but it would take some luck.
Invest in pot, lots of pot, enough to keep you mellow even in large crowds. Always be stoned, your cover depends on not going Hulk. Invest in an internet startup. Become rich enough to start up some companies (this is the luck part). Start up a successful space research company (takes more luck, or at least a fanatical level of determination to see it through). Create some truly massive rockets. Begin many other companies with philanthropic goals to get a following with religious, unquestioning fervor. Get the company to the point where it is regularly sending interplanetary ships. Get some of your followers to agree to a mission where they attach rockets to space rocks for space mining in orbit around your lunar facility. Attach the rockets to something which is about 60 miles (100km) in diameter.
Do the maneuver perfectly, exactly as you had told your investors, bringing it safely into orbit around the moon... except, once it is hidden from all those pesky earth-based observers by the moon, have the rockets change the path to an orbital slingshot which ploughs the rock into the Earth, wiping out all life other than the few employees you have left in space, who will be easy to mop up.
How would you stop or restrain such a man? Basically the same way as any other man, as I said above. But first, you need to know that you needed to stop him.