That's an interesting thing you bring up Sushi, because I feel that Suyin went easy on her son and went just right on Kuvira. Correct me if I'm wrong but Suyin did offer Kuvira a chance to make ammends--to step down as dictator and let Wu act as King. As Korra said herself, Kuvira should have known what she was doing wasn't right. She built a weapon of mass destruction. She nearly killed them all, and nearly sacrificed Bataar Jr for it. The theme of balance means that in the pursuit of justice, one must be careful not to go to an extreme. Maybe Kuvira's plan was the right one, but to what cost?
Kuvira's fate is left uncertain. She most likely will serve time, perhaps for a long time, but maybe leniency will be given at a later time. In many ways, the finale is open ended. Much like with Azula, that was to be explored later.
Varrick and Zhu Li was also something I heard being discussed as poorly handled. He put her through a lot and worked her roughly, but we learn her long-suffering of him was out of respect, and she stands up for herself and demands to be treated with a lot more respect, as a partner. I thought it was fine, especially since we can speculate that Zhu Li did have moments with him that could have happened off screen seeing as how they are secondary, but connected characters--however, considering the level of respect he gave her (which was pretty low) in their introduction and other places they didn't feel they made a good couple.
You know what was great though? Korra didn't go into the Avatar state during that fight. I think she did when protecting Kuvira and some of the city from the spirit bomb, but otherwise that was Korra using her own moves throughout most of the fight.
Also, does anyone have any speculation the time that passed between Kuvira's being taken in and Varrick's wedding? I don't think they would have done so days after the Battle of Republic City. I feel like it would have taken place some time AFTER the city's recovery period. I would hope so at least, because while people criticize Korra's decision to go on vacation for however long, having a wedding while people are still left without homes or infrastructure would be poor taste. Many of the guests, including Lin Beifong, are important members of Republic City and should have been busy at work. I mean, it wasn't so large-scale a wedding that it couldn't have been arranged while things were still getting together, but they also used fireworks that would have been kind of mean since I would expect people would be jumpy.