Direct opposites:
* Disembark: This is the most direct opposite, meaning to leave a vehicle, especially a ship or aircraft.
* Abandon: To give up or leave something completely, especially something you are responsible for.
Other words with opposite meanings:
* Desist: To stop doing something.
* Refrain: To avoid doing something.
* Withdraw: To pull back or retreat.
* Terminate: To bring something to an end.
* Cede: To give up control or possession of something.
* Forgo: To give up something.
The best antonym for "embark" will depend on the specific context of the sentence.