abstrusest
adj. C2 Proficiency ab·strusest
adj. the most difficult to understand or the most complex in a way that is hard to follow.
adj. the superlative form of 'abstruse', meaning the most difficult to comprehend or the most obscure in meaning.
This is the most abstrusest part of the book.
The professor's lecture was so abstrusest that even the most advanced students struggled to follow the logic.
Among the many abstrusest theories proposed by the philosopher, this one remains the most difficult to prove due to its reliance on abstract mathematical concepts.