Give a antonym for the word defend?

Here are some antonyms for "defend", depending on the context:

Direct opposites:

* Attack

* Assault

* Criticize

* Condemn

More nuanced opposites:

* Abandon

* Betray

* Surrender

* Compromise

* Neglect

* Yield

The best antonym will depend on the specific situation. For example, "attack" is a direct opposite if you're talking about physical defense, while "abandon" might be more appropriate if you're talking about defending someone's honor.