So they're basically Tyranids/Bugs/Zerg, except not actually much more dangerous than humans?
I kill them the same way I'd kill humans.
Actual Tyranids - Oh god, we're screwed.
Bugs - Get big guns and fight guerrilla war.
Zerg - Get big guns and fight guerrilla war.
Necrons - We're doomed or enslaved and there's nothing we can do to stop it.
Tau - Diplomacy, or we're probably screwed, but get big guns and fight guerrilla war.
Orks - Kill tons of them and eventually get overrun.
ID4 - Get Jeff Goldblum and Will Smith to take out their shields.
War Of The Worlds - Get a cold, cripple aliens.
Chitauri - We're probably screwed, but get big guns and fight guerrilla war.
Adeptus Astartes - Surrender to our masters and join the Imperium Of Mankind.
Skrulls - Can't really fight Skrulls....
Protoss - Try and work it out peacefully.
Craftworld Eldar - Try and work it out peacefully.
Dark Eldar - Kill as many as possible and cripple their force before they build the momentum needed to win
DC Martians - Diplomacy/Flamethrowers. Lots of fire.
Kree - Surrender to the Kree Empire, since we can't win.
Barsoom Martians - Diplomacy/Fight guerrilla war.
Goa'uld - Kill them.
Replicators - We're pretty much screwed if they want us dead.
Wraith - Kill them.
Falling Skies aliens - Shoot them.
3rd Rock From The Sun aliens - Hang out with them.
Stargate Universe aliens - Fight back, but we seem pretty much screwed.
Autobots - TEAM UP!
Decepticons - Team up?
District 9 aliens - Steal their badass mechs.
The Asgard (Stargate) - TEAM UP!
Asgardians (Marvel) - TEAM UP!
I kill them the same way I'd kill humans.
Actual Tyranids - Oh god, we're screwed.
Bugs - Get big guns and fight guerrilla war.
Zerg - Get big guns and fight guerrilla war.
Necrons - We're doomed or enslaved and there's nothing we can do to stop it.
Tau - Diplomacy, or we're probably screwed, but get big guns and fight guerrilla war.
Orks - Kill tons of them and eventually get overrun.
ID4 - Get Jeff Goldblum and Will Smith to take out their shields.
War Of The Worlds - Get a cold, cripple aliens.
Chitauri - We're probably screwed, but get big guns and fight guerrilla war.
Adeptus Astartes - Surrender to our masters and join the Imperium Of Mankind.
Skrulls - Can't really fight Skrulls....
Protoss - Try and work it out peacefully.
Craftworld Eldar - Try and work it out peacefully.
Dark Eldar - Kill as many as possible and cripple their force before they build the momentum needed to win
DC Martians - Diplomacy/Flamethrowers. Lots of fire.
Kree - Surrender to the Kree Empire, since we can't win.
Barsoom Martians - Diplomacy/Fight guerrilla war.
Goa'uld - Kill them.
Replicators - We're pretty much screwed if they want us dead.
Wraith - Kill them.
Falling Skies aliens - Shoot them.
3rd Rock From The Sun aliens - Hang out with them.
Stargate Universe aliens - Fight back, but we seem pretty much screwed.
Autobots - TEAM UP!
Decepticons - Team up?
District 9 aliens - Steal their badass mechs.
The Asgard (Stargate) - TEAM UP!
Asgardians (Marvel) - TEAM UP!