Final answer:
The word 'milksop' is the closest match to 'weakling,' as it specifically denotes a person who is timid or lacks strength and courage.
Step-by-step explanation:
The word "weakling" refers to a person who is physically or emotionally weak. Among the options provided, the word "milksop" is a synonym for weakling. It's an old-fashioned term that implies a person is timid or lacks courage and strength. The term "namby-pamby" also matches fairly well as it refers to someone who is lacking in character, strength or decisiveness.
Although "baby" and "lightweight" might suggest weakness, they are less precise as "baby" can refer to an actual infant or be used as an endearing term, and "lightweight" often refers to someone of small stature or someone not taken seriously in a particular context.