冤 yuān

冤 yuān means to suffer an injustice or be wronged.

If you look at the oracle bone script of the character you'll see why, it's a picture of a rabbit in a trap:

(Left is the oracle bone script (3,000 years ago), right is seal script (2,000 years ago))

As you can see from the seal script above, this was soon turned into a compound ideogram (會意字) of rabbit (兔) and trap (冂 jiōng).

So just as the blameless rabbit is unfairly caught in a trap, so 冤 means injustice,

冤枉 yuān wang to accuse wrongly, unjustly

And a feeling of being wronged (委屈 wěi qu) can lead to hate (仇恨 chóu hèn), so we get:

冤家 yuān jia enemy, foe