The powerful liquid invented by the professor had a limitation that hindered its effectiveness. The limitation was:

- Short Duration of Effectiveness: The liquid's effects would only last for a short period of time before wearing off. This meant that the benefits of the liquid were not long-lasting and required frequent reapplication.

- Need for Regular Application: Due to the short duration of effectiveness, users had to apply the liquid regularly in order to maintain its benefits. This could be inconvenient and time-consuming for individuals who were seeking a more permanent solution.

- Lack of Permanent Results: The liquid's temporary effects meant that it could not provide a permanent solution to the problem it was intended to address. This limitation made it less desirable for individuals looking for long-term solutions.

- Potential Side Effects: There was also a risk of potential side effects associated with the regular use of the powerful liquid. Users had to be cautious and vigilant about any adverse reactions that may occur.

Overall, while the powerful liquid invented by the professor had its benefits, its limitation of short duration of effectiveness and lack of permanent results made it less appealing to individuals seeking a long-term solution.