General "against":
* laban sa (formal)
* kontra sa (informal)
Against a person/entity:
* laban kay (formal)
* kontra kay (informal)
Against something (object/idea):
* laban sa (formal)
* kontra sa (informal)
* tutol sa (against something you disagree with)
Against a force/influence:
* laban sa (formal)
* kontra sa (informal)
Against a direction:
* laban sa (formal)
* kontra sa (informal)
Examples:
* Laban sa kaaway (Against the enemy)
* Kontra sa proyekto (Against the project)
* Tutol sa panukala (Against the proposal)
* Laban sa daloy ng trapiko (Against the flow of traffic)
It's best to consider the specific context and choose the most appropriate word.