to cause one person to argue or fight with another person

This war has set neighbour against neighbour. 这次战争使邻国之间反目成仇。

to consider something in relation to another thing and compare their different qualities or effects

You have to set the advantages of the plan against the disadvantages. 你得权衡一下这个计划的利弊。

to use or record one thing, especially the cost of something, in order to reduce or remove the effect of another

The cost of business travel and entertainment can be set against tax. 出公差和因公娱乐的费用可以不纳税。