To become a professional Impostor in among us online, you need to be subtle in every step and have the ability to manipulate skillfully. First, the most important thing is to stay calm and not show panic when being suspected. Participate in fake missions naturally, observe how other members work to imitate convincingly.

Second, choose your target and attack time wisely. Don't kill too fast or too slow, and try to do it in places with few people. Don't forget to use systems like doors and cameras to avoid being caught or create an opportunity to escape.

Finally, when participating in discussions, you need to make reasonable arguments and avoid being too defensive when questioned. Sometimes, gently blaming or shifting suspicion to others is also an effective tactic.

Overall, patience, strategic thinking, and the ability to misdirect are the factors that make you the most formidable and unpredictable impostor in Among Us.