How do I make a really "good" antagonist? I like the Idea that they should have a motive, as in my novel, the current antagonist needs to inhabit earth so his race can prosper But what makes a really great story antagonist?
I suggest you to take a look at this great analysis of the Joker in "Batman the Dark Knight": https://youtu.be/pFUKeD3FJm8
Basically, these are the main elements:
- the antagonist has a strong desire and intention, as much as the protagonist
- this desire and intention are in conflict with the protagonist's ones. They are mutually exclusive: if you win, I lose. The world is literally "too small for both of us".
- the antagonist makes leverage on the hero's weaknesses. They act as a relentless opposition to the hero, undoing all the hero's efforts.
- they are strong, skilled, tough: they are the hardest obstacle ever faced. In a videogame, they would be "the boss": after easily defeating dozens of minions, the final fight is generally much harder, and likely to fail.
- their actions question the very core of the protagonist's world view and values.
- the antagonist has a strong logic: you can despise the motives, but you cannot disagree with the logic. You empathize with the antagonist, because you understand their reasons and nature, even if you don't like them.
This depends on your goals and desires for the emotional trip that a reader may go through in your story. Take a look at Game of Thrones. We have characters like Ramsay and Joffrey who were antagonists. They were good though because they were someone you can hate. They were doing many bad things to good people. Everything about them made you want to punch your T.V. in hopes that you could hit them too.
Then we have stories like The Martian or Castaway where the antagonist is not a person at all but the environment, time, nature, their own self and not letting despair take over.
It all depends on how you want the story to be. Do you want to make the antagonist evil? maybe the antagonist wants to take over earth but is doing it out of necessity with no other choice and is actually a really nice being. If the story was told from his POV, he would be the protagonist and the earthlings would be the antagonists who are getting in his way of saving his race.
It really does boil down to how you want the story to flow and how you want the "bad" guy to be presented.
A quick google came up with this link that may help you refine your needs of how to write a better antagonist. There were several links that came up with an easy google search: How to create a good antagonist.
This is another question which is (a) Too broad. (b) Does not take into account the subjectiveness of "good".
Your plot is well-used and has proven difficult to incorporate a detailed antagonist due to difficulty of communications.
In "War of the Worlds" they pretty much wanted to destroy us and didn't want to talk about it. "Independence Day" was more of the same. "The Day Earth stood still" featured a plot in which we were the bad guys.
The TV series "V" didn't really follow the single hero / villain plot as there were good and bad on both sides.
The difficulties in providing backstory and showing interaction between protagonist and antagonist may be one of the reasons than S/F novels are traditionally shorter than others. Alien invasions are particularly difficult to handle because when people are coming to destroy you . . . you don't really care why.