In the following question, choose the one-word substitution for the phrase: "One who is determined to take full revenge for wrongs done to him".

Introduction / Context:
One-word substitution questions test your ability to replace a long descriptive phrase with a precise vocabulary item. The phrase given here is "One who is determined to take full revenge for wrongs done to him". In everyday and literary English, such a person is described by an adjective that captures a spirit of strong, often unforgiving revenge.

Given Data / Assumptions:

• Phrase: "One who is determined to take full revenge for wrongs done to him".
• The task is to select the best single-word substitute.
• Options include nouns and adjectives related to behaviour or attitude.
• We assume the focus is on a strong desire to retaliate, not on general dislike or mere hostility.

Concept / Approach:
The key idea in the phrase is an intense, persistent desire to take revenge. The standard adjective for a person with such a mindset is "vindictive". A vindictive person is not merely angry; they hold grudges and actively seek opportunities to punish or hurt those who have harmed them. The other options either describe different qualities (such as cowardice or learning) or refer to relationships that do not capture this specialised sense.

Step-by-Step Solution:
Step 1: Focus on the core meaning: "determined to take full revenge" suggests a strong, perhaps excessive, revenge-seeking attitude.Step 2: Examine "Enmity" (option A). This is a noun meaning hatred or hostility, not a person and not necessarily someone actively seeking revenge.Step 3: Examine "Pedant" (option B). A pedant is someone overly concerned with rules or minor details, unrelated to revenge.Step 4: Examine "Coward" (option C). This word denotes someone lacking courage; such a person is unlikely to be determined to take revenge.Step 5: Examine "Vindictive" (option D). This adjective describes someone who is strongly inclined to seek revenge, exactly matching the description.Step 6: Examine "Benefactor" (option E). A benefactor is someone who helps others, usually in a generous way, the opposite of a revenge-seeker.

Verification / Alternative check:
Dictionary definitions confirm that "vindictive" means "having or showing a strong or unreasoning desire for revenge". The phrase in the question emphasises determination to take full revenge, which aligns perfectly with this definition. If we try to replace the phrase in a sentence—"He is a vindictive man"—the sense that he is full of revengeful feelings is clear. None of the other options express this idea. Therefore, "vindictive" is the only accurate one-word substitute.

Why Other Options Are Wrong:
"Enmity" describes a state of mutual hatred, not a person or personal quality. "Pedant" focuses on academic or rule-related fussiness, not emotional revenge. "Coward" is about fear and lack of bravery. "Benefactor" means someone who gives help or money, which is the opposite of trying to hurt others. None of these words convey the sense of vengeful determination described in the phrase.

Common Pitfalls:
Some candidates look only for words that appear negative and may choose "enmity" or "coward" because they sound unfriendly. However, one-word substitution questions require very precise semantic matching. It is helpful to learn key adjectives such as "vindictive", "benevolent", "malevolent", and "magnanimous" with their exact shades of meaning. This builds a strong vocabulary base for exams and prevents confusion between general hostility and specific revenge-seeking attitudes.

Final Answer:
The correct one-word substitute is Vindictive.