It’s easy to make the word "help" into an adjective. Just add the suffix "less" to "help." A person feels "helpless" if he or she has no control over a situation.
She feels helpless without her cell phone.
Ali felt helpless without his wife at home.
People who don’t know a lot of English sometimes feel helpless in English-speaking countries.
The man who lay weak and helpless by the side of the road was in need of medical assistance.
You can make this word into a noun by adding yet another suffix, "ness" to make "helplessness."
Oliver was overcome by a feeling of helplessness after his father died in a car accident.
Some people believe that the welfare system in the United States leads to a condition of learned helplessness among those who receive benefits.
Note: The direct opposite of "helpless" is not the word "helpful." A better opposite adjective might be "powerful" or "strong."