The pair "VINDICTIVE : MERCY" represents a relationship where one word is the direct opposite or contrasting quality of the other. "Vindictive" describes a tendency to seek revenge, while "mercy" represents compassion or forgiveness, which is the opposite quality.

So, to find a similar relationship, we need a pair where one word is the direct opposite of the other:

E. skeptical : trustfulness

In this pair, "skeptical" (doubting or questioning) is the opposite of "trustfulness" (willingness to trust). This reflects the same kind of contrasting relationship as "vindictive" and "mercy."