Well, first thing to do is to find out what units the superpower is using. To have a chance at beating them, you'll need to make units that specialize at defeating their units. For example, if they use lots of medium tanks, then you'll want to produce anti tanks, tank destroyers, and attack bombers. DON'T FORGET RESEARCH!!

But to mass-produce units, you need a good economy and lots of resources. Build industries and industrial complexes and level them up, and if there is a resource you are short on, use the stock market, or better yet, trading with your allies.

Next, you'll want to get a couple of other countries to help you with the attack. Since the superpower (probably) has a strong army, they would be able to easily defeat you alone. Getting 2 or 3 others to attack the superpower makes him have to fight across multiple fronts. Make sure you have share map with them, or at least right-of-way.

If you have money to spare, you might want to dispatch a few economic sabotage spies in his core cities or other cities of his that have high-level unit production buildings, further slowing his production.

When you start the attack, the first things you want to do are 1) take out his main (strong) units, and 2) capture his key producing cities. If you do so, it will halt his production of both units and resources. Air superiority is important, so make sure to be producing lots of interceptors and tactical/attack bombers, depending on what kind of units the enemy is using. If the enemy is using naval units, then you should produce units to counter their units (ex. if they have lots of battleships, make submarines & naval bombers)

Keep attacking the enemy's units and taking their provinces, using your normal attack strategies, and tailoring them to fit the current situation. Remember to communicate with your allies - you might want to make a coalition, or join theirs, if they have one. Once it seems that you have taken out most of their units, capture their remaining cities, and any weird provinces you didn't take. You might want to communicate with your allies and discuss who gets what territory, to make sure nobody isn't satisfied. If you have made a coalition, you might have enough VPs to win the round, if you don't, keep attacking other countries with your allies until you do.

That's pretty much it

Well, first, a superpower USUALLY, but not always, became a super-power because he was a good player to start with - so there is no "easy trick". Exceptions : gold users, and historical maps.

I see four things to take into account :

- What is the long term dynamic of the map. By long term dynamic, I mean that there are always AI and minor players around, within reach of either you // your coalition or off the superpower. If each of you take-over those territories, who will have the best production ? If you have the advantage doing this sort of calculation, you know what you have to do : grab those territories as fast as possible while stopping him from starting to grab stuff in your perimeter (which won't be easy of course), then play the long game.

Another dynamic is what I would call the industrial dynamic : if he has better industry but is occupied somewhere else, maybe you can only build the minimum units necessary to hold the line, and industrialize as fast as possible to catch him up.

- There are two axis in the game, land (+air) and naval (+air). A superpower that is great at both can be beaten if you focus on only one. For instance, you can forgo FULLY shipbuilding, except for a few submarines to keep him on his toes and spot enemy transport, and only build as massive an army as you can. Maybe at some point you will need a navy, but if you take EVERYTHING that can be taken by your army, then maybe later you will be able to pivot.
You WILL need a strong airforce and mobile troops (and I recommand an heavy infrastructure networks) to counter the enemy landing, but I believe it can be done.

On the other hand, if your opponent abandoned sea power, there may be a way to make him pay for that. In the Lets Play in my signature, my coalition and the hostile coalition where more or less at parity on the old continent for land force, with a dynamic going against us due to their South American ally who had his own army AND a lot of room for growth. Nonetheless, the enemy had lost all their fleet, which allowed my coalition to seize Madagascar, which was immediately endgame as the enemy coalition understood (they quitted) even though we did not put a foot in Africa proper : the enemy core was at range of ballistic missiles, and we could land wherever we wanted.

- This was actually the third item : the game has a geography : natural obviously (a failed crossing of Suez can turn a game around) but also "political" : maybe two AI players have built so much units that no players want to go through, create a wall or a chokepoint, or maybe that other AI player on the side of your enemy has "free passage" with you from the time where this guy was a player. Use it. I actually never manage to pull that in end game, but I broke a stalemate in medium-end game by going embarking my troops from "neutral" territory (Ethiopia) to land during my opponent night in his territory, bypassing his way stronger fleet.

And something else about geography : typically superpowers have core FULLY 100% developed, and for rest only 2 icons city are develop. If you manage to reach the core the game can turn. Of course easier to do against Japan than against Tibet.

- Last item : use diplomacy, especially if the "superpower" is in coalition with weaker player. It is pretty easy to convince someoen that the superpower wants to do a solo win (if he has solo win in his profile, claim that clear he prefers to win solo ; if he has none tell them that probably the guy will want to secure his first solo win - wouldn't you ?). I never fully pulled out (though see my signature for managing to keep Nigeria out...) but I lost a game where I was the major power of a coalition because one of my crafty opponent turned one of my allied against me at a critical moment, in order to destroy my air fleet as it did transition through my "ally" airport. Well played, Germany. I still remember it. Xianjiang, pray God never to be in a game with me again :).

Oh. You have lost. There is not really room for 3 players in South America in my opinion, it stops you from reaching critical size.

Your only hope is try to convince someone that whoever leads the coalition is going to fly solo, but given it seems well balanced good luck with that.

hate it when people do this to me

Hi, right now i'm in the all countries all in and the superpower i'm going up against is sweden (im libya) and he has taken out pretty much all of europe including romania and another powerhouse (france) I can sustain a war of attrition I produce enough troops to invade him and keep a front but i'm currently retreating & trying to make peace with him because its hopless, I am an experinced player but right now I am kinda at a road block I need help, anyone got any advice on what to do? (also he seems a little reluctant to go all in on an invasion of me, maybe because i'm allied with smaller super powers & bigger superpowers than him)

You gotta help me out here, what is a "smaller superpower" than Libya?

I think that perhaps he meant smaller than Sweden.