The most painful tooth to extract is the Wisdom tooth and any other impacted teeth.
Wisdom teeth are very painful to extract because the wisdom teeth are located near major nerves and can be impacted with means it hasn't erupted properly.
The procedure to extract wisdom teeth is also complex and the root structure is often curved and has multiple roots which also makes it more difficult to remove.
Tooth decay and other previous restorations can also make a tooth fragile and more difficult to extract.
Due to their location and anatomy the lower molar teeth are typically the most difficult to extract.
Lower molar teeth have multiple roots, making removal from the jawbone more difficult.
Furthermore, the roots of lower molar teeth are frequently curved or twisted, making extraction more difficult.
Many of your front teeth are round, so they can often be removed without damaging any bone quite easily.
However most of your back teeth also have two or three roots and cannot just be “pulled out” without breaking something which makes them more difficult to pull.
A myth that the rotten teeth are easier to extract stems from the mistaken notion that weaker structures require less effort to remove.
In reality, the extraction process for rotten or dead teeth is more nuanced and affected by the tooth's condition, surrounding tissues, and overall oral health.