"Defeat the Queen" is the last mission objective in the game Aliens: Colonial Marines
This is it. You must defeat the Alien Queen
1) You first have to reset the Catapult the by activating all 4 Manual Reset Switches. Be on the move all the time so that the Alien Queen doesn't catch up to you. Find shelter in containers and behind other cover. Use your Motion Tracker to see the location of the current Manual Reset Switch that needs to be reset.
2) After all switches have been reset, go to the Cargo Launcher Release
3) Lure the Alien Queen to the tracks in front of the Cargo Release.
5) If the Catapult missed, repeat steps 1-4 again.