Some years back, probably close to 3 decades, Avalon Hill made a card game called Naval War. Now the basic idea of the game was simple enough, you had to be the player who sunk the ship to score the points for that ship. However, as no single attack could sink a ship you had to be careful to avoid crippling a ship and having the next player sink it and take the points.
So with that in mind, you score points for being the player who eliminates another players character, for a number of points equal to the characters cost and upgrade cost in resources of any attached Upgrades at the point you eliminated that character.
A player who survives gains the value of his surviving characters and upgrades.
I would suggest that you play at least 3 games and keep a running total, which also ensures that players will gang up on the player who is winning and create a whole mess of aggravation for that player.
Edited by Amanal