The Flash season 7 finally put Killer Frost on trial for her past crimes, making it an important one for the Arrowverse. While Caitlin Snow's Killer Frost persona began her time in the Arrowverse as a villain, the icy metahuman eventually went in a more heroic direction. Despite her good deeds in the last few seasons, it didn't erase the crimes Killer Frost committed, as The Flash season 7 finally decided to tackle that unresolved storyline. As she turned herself in, The Flash season 7, episode 8, "The People v. Killer Frost," saw Caitlin's other half go to trial to answer for her criminal past. While Killer Frost was ready to face her punishment, Team Flash wasn't prepared for the prosecution's aimed punishment.
Rather than have Killer Frost serve 10 to 20 years in prison, they wanted to use the Arrowverse's metahuman cure to remove her powers for good. The cure could potentially harm or kill Frost, due to her being created through meta-DNA. While it turned out that it wouldn't end Killer Frost's life, she still requested the court to be sentenced to prison for life without any chance for parole. However, Killer Frost discovered Kristen Kramer's big grudge with metahumans, as she wasn't specifically targeting Frost, but all metahumans who would use their powers to commit crimes. Killer Frost pleads to the court that the cure shouldn't be used as punishment to remove a metahuman's abilities when it's their actions that should be held accountable.
This leads to Killer Frost's request to serve life in prison granted, which was the right direction for this Arrowverse storyline, for two big reasons. Having Frost walk free, but without her abilities, would be a massive disservice to this arc that The Flash season 7 has spent multiple episodes on this year. Frost's criminal past is something the show should have tackled several seasons ago. Nevertheless, the fact Frost's trial concluded with her going to prison, potentially concluding her time on the show, allows this Arrowverse plot to be properly finished. Obviously, Frost will probably be seen a few more times this season, but not in the same capacity.
But the other significant reason for Frost's story to end like this is because of the problems that would come with the metahuman cure. Just because a criminal metahuman would lose their powers, that wouldn't mean they would stop breaking the law, if allowed to walk free. The fact the prosecution wanted to let Frost walk free, at the cost of her powers, is problematic. All it does is let Frost have no powers, which is a small price to pay for her past crimes during the earlier seasons of The Flash. Even if Frost saw it as a game-changer, it doesn't allow her to pay her dues to society.
From now on, The Flash needs to stay true to this storyline and actually have Killer Frost be in prison. It would be a massive injustice if the seventh season somehow undoes it and lets her walk free, despite being sentenced to life in jail without parole. Otherwise, this Arrowverse storyline will have been a complete waste of time. That doesn't mean we shouldn't see Frost from time to time, through Caitlin Snow or other characters visiting her. Since The Flash also decided to split Caitlin and Killer Frost into two separate characters, if the latter somehow isn't forced to serve her time, then it's another wasted plot point for the Arrowverse.