Hudson seems to be pretty intent on remaining the publisher with the most games on WiiWare. I wonder when these will come out...
I got stuck on Onslaught on a particular stage when the difficulty ramped up pretty sharply after the first boss.
That's why you're still a kid! (I assume you mean the base defense one, use the tank to snipe the far-away hives, some are slightly hidden and might require a bit of moving but don't bother with the south hive yet. Snipe the jammer bugs too while you're at it. When you have 3 minutes left on the clock the enemies stop spawning until 2 minutes left to give you some time to deal with the remaining hives, should only have the south one left, wreck it and on the way back go through the crates on the south edge of the base, you'll find the lv2 assault rifle there, if you still can't beat it then leave the tank after sniping the hives, fend the enemies off with your regular weapons until the 2:00 assault, hop in the tank then and finish it)