to beat 2.5 just keep building fusion cores and gauss cannons. Simple as that. For 2.6 build 3 fusion cores and wait until you can build a bomber. After you switch to bombers simply defend and repair and allow your bombers to do the work. should be a couple minute battle.
People should take the time to learn about the game before they complain. Most weapons have a very limited supply of ammo. Rocket launcher is powerful but you get 3 shots and a long reload. I personally think its a well rounded game other than there are times when you can get stuck in a bad respawn point and die quickly.
FINALLY got the hard badge. Damn. Play defensive and keep your fighters in reserve until all naval units have been destroyed. Use the fighters as blocking units and keep a rocket truck behind them for long range. Eventually the enemy will get worn down enough you can use the fighters to thin the ranks enough to send a couple big tanks to take out turrets or make a battleship to dominate the land.
for boosts its super easy once you get sir collin and just do flips like mad. Hard to control but once you get the hang of him he is just about the best for most races.