What is a brief overview of Imam Abu Hanifa and his madhhab, and why do some disparage his madhhab for relying on qiyas (analogical reasoning) and opinion?

Abu Hanifa al-Nu'man ibn Thabit al-Taymi al-Kufi, the jurist of the nation and the scholar of Iraq, was born in the year 80 AH and saw Anas ibn Malik. He was known for his dedication to seeking out traditions (athar), his excellence in jurisprudence (fiqh) and juristic reasoning (ra'y), his eloquence, piety, and devotion. He died as a poisoned martyr in the year 150 AH.

The Hanafi school of thought is one of the four famous and the earliest jurisprudential schools. It is based on the ijtihad (independent reasoning) of the imams in understanding the evidence from the Quran and Sunnah. Imam Abu Hanifa expanded on the use of juristic reasoning (ra'y) and analogical deduction (qiyas) in matters other than prescribed punishments (hudud) and expiations (kaffarat), due to his limited narration of hadith and his strictness stemming from the prevalence of fabrication in his era in Iraq. It is worth noting that the Hanafi school is not composed solely of Abu Hanifa's opinions; rather, it includes the opinions and ijtihad of his students, which may later be adopted as part of the school.

The differences among the jurisprudential schools are attributed to the varying accessibility of hadiths and evidence to the imams, or their differing views on the authenticity of chains of narration. Nevertheless, the four imams, including Abu Hanifa, unanimously agreed that an authentic hadith is their madhhab (school's view), that it is not permissible for anyone to adopt their sayings without knowing their evidence, that any of their sayings contradicting the Quran and Sunnah should be abandoned, and that everyone's saying can be accepted or rejected except that of the Prophet, peace and blessings be upon him.