pushover
A person who gives in too easily to others.
A pushover is someone who gives in too easily when others pressure them or make demands. If your friend always lets other kids cut in front of them in line, or agrees to every request even when it's unfair, they might be acting like a pushover.
The word creates a clear picture: imagine someone so weak they could be pushed right over with barely any effort. A pushover doesn't stand up for themselves or say no, even when it would be better for them to do so. If someone keeps asking you for answers on schoolwork and you say yes even though you know it's wrong, you're being a pushover.
Pushovers often let others take advantage of them because they're afraid of conflict or eager to please everyone. People may lose respect for pushovers, and pushovers may feel resentful later about situations they didn't stand up against.