Q:

Can you kill a golem with passwall?

Assuming you're within range of a golem can you cast passwall on it to kill/destroy it?

A:

You create a passage through wooden, plaster, or stone walls,

(emphasis mine)
A golem is not a wall, no matter what it is made of, and therefore passwall does nothing to it.

A:

Passwall doesn't do damage. I can see an argument whereby you might be able to open a hole through an especially large golem or colossus, if it were large enough to be perceived as a "wall", but this wouldn't actually harm the golem, just change its shape temporarily.
I can see some possible creative uses for this effect. For example, you could order a golem to plant itself between you and an opposing party, open a hole to shoot arrows or spells at your opponents, then close it again to gain cover. But in terms of actually destroying the golem, I don't think it would work.

