well I m not sure abput the following situation.

2 Players fight. 1 Player loses all of his unit-cards. does he instantly lose the battle or may he win the battle, if his points add up to a higher score than villian´s score.

He does not instantly lose the battle. If he still has a combat bonus (from cities, Academys, Great Generals, etc...) higher than the total strength of his opponents units, he still wins. It is important to note that even in this instance, if he had more than one Flag figure in the battle and lost two or more unit cards, he loses one Flag figure for every two unit cards lost (to a minimum of one).