Batman has several rogues that present many different and unique challenges. Killer Croc and Bane push the Dark Knight to the upper limits of his physicality. The Penguin forces Batman to find legitimate ways to destabilize his large reach and criminal empire. The Joker creates a need for Batman to expect the unexpected and find the means to contain the Clown Prince's chaos. However, The Riddler is the one who perhaps challenges Batman the most intellectually... but have those days passed? If you look at Riddler-centric Batman comics since the New 52, many of the ones that take place earlier in Batman's career seem to be the most dire, while more recent conflicts with Edward Nygma have seemed like no problem at all for the Dark Knight.
The Riddler is obsessed with puzzles and challenges designed to stump his victims and prove him the intellectual superior. The consequence is that he always leaves opportunities for his plans to be thwarted, as there's always an answer to solve his riddles. Batman has become extremely proficient at solving the quandaries presented by Nygma, which drives the Riddler to intense anger and further obsession, making it his life's goal to unequivocally prove once and for all that he is better and smarter than the Dark Knight. However, it seems as though Riddler's attempts were stronger and more successful back when Batman first began his career, as seen in the Zero Year and The War of Jokes and Riddles story arcs.
In Zero Year, from Scott Snyder and Greg Capullo, the Riddler was one of the first rogues Bruce Wayne faced while stepping into his Batman persona. Riddler got incredibly far in his goals of taking over Gotham, flooding the entire city leaving it without power and Batman unable to stop his plans. Nygma then turned Gotham into his own personal domain, taking control of the city for nearly an entire year. Every day he would search for a worthy opponent to his intellect, asking for challengers on a giant jumbotron in Gotham Square, though he wouldn't find one until Batman reemerged. Eventually, Batman, Gordon, and Lucius Fox manage to get power back to the city and regain control. Batman had to go through a gauntlet of riddles, and then restarted the city's power with his own heart, thereby defeating the Riddler, though the act nearly killed him.
Likewise, in The War of Jokes and Riddles, which took place in Batman's second year, from writer Tom King, Riddler gathered forces and went to war with Joker and his allies. Nygma initially convinced Batman to side with him, marketing himself as the lesser of the two evils. However, he drove Batman to his limits with the reveal that he orchestrated the entire war in an attempt to make Joker laugh. As a result, Batman almost broke his one rule and tried to kill the Riddler, if not for the Joker intervening.
Essentially, since the creation of the New 52, Riddler has been crafted as a more serious threat than he's been characterized in comics past. However, the problem is that both of these stories described take place in Batman's first few years on the job. The most recent and significant Riddler appearance besides those stories was in Their Dark Designs, a prelude to the current Joker War arc from James Tynion IV. In that story, Riddler's role in the Designer's plans was to create a traffic gridlock, forming a giant massive crossword out of Gotham's city streets. However, Batman solves the crossword with extreme ease, with the puzzles barely posing a problem for the Dark Knight. It almost seems as though Riddler no longer poses a threat anymore at this point in Batman's career with all the experience he's gained. This shouldn't be the case. Riddler is too intriguing a character (as Matt Reeves' The Batman trailer shows). Hopefully the next great Riddler epic will prove that he hasn't already peaked as a Batman villain.