Human Campaign Level 15
This level is relatively easy, but since some people have trouble going through this level, I guess I would put up a quick walkthrough on this.
The level starts off in the Dome. Make sure to grab powerful weapons like Rocket Launchers in the beginning few seconds. After getting a Rocket Launcher, go around killing off the Commanders quickly with either the Holy Grail or a Rocket Launcher. As these Commanders can teleport, make sure to shoot fast without delaying. While killing off aliens, continue moving around the map. Grab the power-ups scattered around the field to kill more efficiently. Just keep on killing any alien on sight and you should be done. Don't hesitate to kill your teammates along with the Commanders if needed.
Alien Campaign Level 11
Artifact Retrieval 101 is actually pretty easy if you are fast. Set in the Facility stage, this place has water. When the game starts, quickly get to the Invincibility power-up while getting a Rocket Launcher. Holy Grail will not do here. When you get the Invincibility power-up, quickly get to the base for the humans, kill everyone and get the flag. Rush down and voila! Just keep doing this and you will have this in the bag!
More coming soon