The opposite of ISTJ in the Myers-Briggs Type Indicator (MBTI) is the ENFP. ISTJ stands for Introverted, Sensing, Thinking, and Judging, while ENFP stands for Extraverted, Intuitive, Feeling, and Perceiving.

1. Extraversion vs. Introversion: The most apparent difference between ISTJ and ENFP is their preference for extraversion or introversion. ISTJs are introverted, meaning they tend to focus their energy inward and gain energy from spending time alone or in small groups. On the other hand, ENFPs are extraverted, meaning they gain energy from being around others and enjoy socializing and interacting with a wide range of people.

2. Sensing vs. Intuition: ISTJs rely on their sensing function, which means they prefer to gather information through their five senses and focus on concrete details and facts. They are practical and prefer to work with what is known and proven. In contrast, ENFPs rely on their intuition function, which means they are more interested in patterns, possibilities, and future-oriented ideas. They enjoy exploring new concepts and are comfortable with ambiguity and abstract thinking.

3. Thinking vs. Feeling: ISTJs primarily use their thinking function, which means they make decisions based on logic, objective analysis, and rationality. They value fairness, consistency, and efficiency. ENFPs, on the other hand, primarily use their feeling function, which means they make decisions based on personal values, empathy, and consideration for others' emotions. They prioritize harmony, authenticity, and emotional connection.

4. Judging vs. Perceiving: ISTJs have a judging preference, which means they prefer structure, organization, and planning. They like to have clear goals, deadlines, and guidelines to follow. They are typically decisive and prefer closure. ENFPs, on the other hand, have a perceiving preference, which means they prefer flexibility, adaptability, and spontaneity. They enjoy exploring multiple options, keeping their options open, and are comfortable with uncertainty.

In summary, the opposite of ISTJ, the ENFP, is extraverted, intuitive, feeling, and perceiving. They differ in their energy source, information gathering, decision-making, and approach to structure and planning. While ISTJs are practical, logical, and prefer stability, ENFPs are imaginative, empathetic, and prefer flexibility.