Warning: The following contains SPOILERS for Superman and Lois season 2, episode 11.
A major DC Comics rule regarding how Kryptonite affects Superman was broken in Superman and Lois, suggesting a different set of physical laws for the Arrowverse. Traditionally Green Kryptonite has been said to render Superman completely powerless, in addition to causing him great pain. However, one scene in Superman and Lois bucked this trend with Kryptonite having a notably different effect to the Kryptonian in the Arrowverse series.
While there are several types of Kryptonite with different effects depending on the color, Green Kryptonite is the most famous. The fact that Green Kryptonite takes away Superman's powers is well-known even to people who don't read comics. Indeed, referring to someone's greatest weakness as their "personal Kryptonite" is arguable just as popular of an idiom in the modern age as the phrase "Achilles' heel."
Despite this, one scene in the Superman and Lois season 2 episode "Truth and Consequences" confirmed that the Arrowverse Superman was far from powerless when exposed to Green Kryptonite. The Jonathan Kent of Bizarro World, Jon-El, launched a sneak attack on Superman which left his chest embedded with Green Kryptonite shrapnel. He also stabbed the Man of Steel with a Green Kryptonite crystal. Superman was incapacitated until Lana Lang was able to pull the shards out of his wounds, but he was still able to hear the often imperiled Lois Lane, as she shouted his name while Jon-El attacked her and their sons, demonstrating that in the Arrowverse, Kryptonite hurts Superman, but does not strip him of his powers as is normally depicted in the comics.
There are many stories which have previously confirmed that Superman becomes powerless when exposed to Green Kryptonite, but the most famous example came in 1997's JLA #4 by Grant Morrison, Howard Porter, and John Dell. The story pitted Superman and the rest of the World's Finest heroes against the Hyperclan, a group of aliens who posed as a team of heroes while secretly working to conquer Earth. Captured by the Hyperclan and exposed to a piece of Green Kryptonite, Superman was seemingly helpless while the Hyperclan tortured his allies. Superman suffered his own subtler form of torture, as he heard billions of voices crying out for help. It was the fact that Superman could still use his super-hearing that clued him in to the fact that the Kryptonite before him was a telepathic illusion and the Hyperclan were secretly White Martians.
This is not the first time that Superman and Lois has suggested that the rules for how Kryptonite works are different in the Arrowverse. In the Superman and Lois season 1 episode "Broken Trust," Clark was able to restrain his heat vision after being wounded by four Kryptonite shards and hold the energy back until he could remove the Kryptonite himself and destroy it with a focused blast. This emphasized how Superman's greatest power may be his sense of self-control, given how much he must hold back to avoid hurting others by accident.
New episodes of Superman & Lois release Tuesdays on the CW.