If "hoist" means to lift something up:
* Lower
* Drop
* Descend
* Let down
If "hoist" means to raise a flag:
* Lower
* Take down
* Furl
If "hoist" means to elevate someone's spirits:
* Depress
* Discourage
* Dampen
So, the best antonym for "hoist" depends on the specific meaning in the context.