By Kuvira Crisis, I mean when she proclaimed the Earth Empire to right before she attacks the UF ships. I might add on as I watch the final two episodes.
The Earth Empire.
Proclaiming TEE: She technically did nothing wrong, as she made an oath to step down from uniting the Earth Kingdom, not, not forming a new Empire.
Slavery and Imprisonment of non-Earthbenders: Slavery I am not sure if it is mentioned for a fact by the Prisoners, but I know it is a rumor. Since it is a rumor i can't really say anything on it. Imprisoning those people though is not good, but they may have lied and commited crimes, but I will assume it is to root out potential traitors, which is also not good. About the Re-education camps, since all that is mentioned is that traitors get sent there, I just think it isn't some torture camp.
Attacking Zaofu and the UR: It is EE territory so it isn't as bad as say, attacking the Water Tribes. UR is worse since it is it's own nation, but it is still EE territory.
Kidnapping Wu: Bad, but isn't as bad as Kidnapping another world leader, since Wu is incompetent at leading.
The Super-weapon: I don't see anything wrong with it. A good way to keep peace is with the threats of facing a super-weapon. Saying TEE having the cannon being wrong, is kinda like saying any Nuclear Power holding onto their Nukes is wrong. While holding onto them is fine, Kuvira using hers is nowhere near as bad as using Nukes, as the cannon's firepower is nothing compared to nukes. Part of this is the taking of vines, which I don't see anything wrong with. They are natural resources.
Lasering those Scouts: They were enemy combatants, kinda. May be wrong, but if I am, then it is wrong.
Everyone Else.
Su's attack on Kuvira: This is consider bad. Su and her attack squad violated the peace treaty between Zaofu and TEE. She attempted to attack Kuvira in her sleep when negotiation where being made.
The 1v1: On a minor scale, Kuvira and Korra's 1v1 was stopped by Opal and Jinora, who where diplomats. Bad, but on a smaller scale. This also may be a Warcrime under the posing as non-hostiles part.
Operation: Beifong: Another bad one. This time the attacked and rescued people who where legally detained.
Another attack on Kuvira: Once again they do another strike. Nothing happens, though they attack again before any war was declared.
Not surrendering: Korra and a small group went against the peace that was the surrender. May be a warcrime under Perfidy.
Attacking Bataar: They attacked and took hostage Bataar, when they where negotiating surrender. Another warcrime.
Might have missed some stuff, but I must say TEE is the lesser evil in the Kuviria Crisis. Simply because the amount of Warcrimes and attacks committed before any war started. It is close though, and this is my opinion.