In most RTS games, if you are doing much better than your opponent, you have a 99% chance of winning. This is not the case in Supreme Commander: if one strategy you are using is giving you a major advantage, your opponent could still be developing a strategy that you are not prepared for and win the game. Here are a couple of examples:
- Player A has about 100 more units than Player B, including about 50 interceptors. Therefore, he has complete land and air dominance. But he leaves his commander out in the open and uses each and every one of his interceptors to guard his gunships that are sent to attack Player B's ACU. Player B takes the opportunity to send his 5 T2 bombers straight for Player A's ACU, located on the other side of the map. Player A, realizing what's happening, tries to send some interceptors to the other side of the map to counter the threat, but it is too late, Player B wins the game using just 5 T2 bombers.
- Player A, once again, has complete dominance of land and has the advantage, and little by little works on destroying Player B's base. He wants to avoid Player B's army at all cost so he can do all he can to Player B's base. But little does he know that Player B, realizing he is losing, is making an all-or-nothing effort to win by stocking up his tech 1 units, and, in a last-ditch effort, sends each and every unit to attack Player A's ACU. The ACU is outnumbered and destroyed.
- Player A has an economic advantage, with a score difference of 6000. His teammate is attacking Player B with a small attack force to ravage Player B's developing economy. Player A is working on a massive fortification in the mountain while Player B has lost a good chunk of his power grid and cannot continue very easily. However, hastily-built AA guns take down the attack force his teammate launched and Player B is working on some T3 bombers. Player A's defense grid has multiple flaws, and Player B flies his Ambassadors around the grid and into Player A's unguarded base, conveniently placed behind the defense grid, out of range from it. Unfortunately, that is also where Player A's ACU is kept. Player B wins (yet again) with only two T3 Bombers.
In other words, don't get cocky. It is important throughout the game to keep pressure on your opponent. If you leave him alone because you want to slow down and relax or build up a strong army, thinking you are going to win hands-down, you are giving your opponent the opportunity to develop a counter strategy, whether it's teching-up, building a strong defense that is completely impassable, sending units through the back door, or anything to that effect.
So to summarize, do not give your opponent the chance he needs. Keep spying on him: if he has a strategy you are not prepared for, you should change tactics as quickly as possible before he gains the upper-hand. If you have a perfect chance to get into his base, take the opportunity before it goes away, even if you only have a small army to do it with. And keep putting pressure on your opponent with numerous small attacks, whenever possible, so that he has to keep guessing what you are doing and spend more time defending himself, leaving him less of an opportunity to do what he wants to do. Control your opponent, don't let him control himself.