"What does he have to gain? Or to lose?"
"This is the worst kind of villain, folks! He has no motivation, no credible backstory, no emotional connection that makes us sympathize or understand why he does the things that he does; he's just some asshole who wants to kill the hero because he's the villain!"
The aliens in Battleship are typical antisocial movie xenomorphs. They exist exclusively to destroy things. There's no motivation. They just show up, play a giant game of "Battleship" (yes, they find a way to shoehorn in a few rounds), help our hero to grow up, then fall prey to a Deus ex Machina.
Dave: So let me get this straight. Your plan was to spend decades of your life and a bajillion dollars to build a time machine so you could go back and steal experimental metatechnology from new genesis just so you could build a machine that brings badfic characters to life? Seriously dude what the fuck???
Monarch: Mwa ha ha ha ha ha ha ha ha ha ha!
Dave: Oh right I forgot. You're a one dimensional cardboard cutout masquerading as a supervillain.
Monarch: And don't you forget it!
"Unicron is given no backstory (until season 3) or justification; he simply exists, is very dangerous, and is afraid of the Matrix, all for no adequately explained reason."