First, you need a LOT of money for this one, and a lot of time. This requires that you do not mind losing a Level 4 or higher citadel (a minimum of 20 days work..) I would suggest approaching this as an extremely violent and expensive way of eradicating the competition. You first must have a Level 4 citadel. Second, you must have enough credits to buy a few Genesis Torpedoes. Third, you must know the location of one of your enemies shield bugged planets. (one or more.. in the same sector that is) Fourth, you must be up late. Buy enough genesis torpedoes so that you can fill the sector of your enemy with planets to the maximum allowed by the game (the usual value for this is 5 planets per sector). Fill it up until TradeWars gives you a message telling you no more planets can be put in the sector.
 
Then place one fighter in your enemy's home sector (that means you must destroy all the fighters there first). Then, go to your Level 4 or higher Citadel planet and TransWarp the planet to the sector where you just put the fighter. The sector is now OVERLOADED with planets. When

the External Maintenance is run, it will either say 'An Unstable Planetary Mass was detected in sector XXX'. Or, if you're lucky, it will say 'DeathLand Alpha collided with planet Enemy's-HomePlanet One' or something to that extent. Sometimes the planets that are bare (that you created with Genesis Torpedoes) will get destroyed or destroy another planet. Sometimes you may be lucky enough to have one of the useless, barren planets you created collide with your enemy's planet, so your Level 4 or higher planet is saved.
 
The reason I say be up late is because most of the time, the External Maintenance program is run at midnight, so you have a MUCH lower chance of your enemy assaulting your Level 4 planet or destroying one of the barren planets.