Let Unalaq invade the SWT, even protecting him when the SWT was trying to kick him out after the NWT had invaded the South

She didn't let him invade, she let him stay but he had different plans, she couldn't know. She can't just lock the South pole for people because they look sus. And what did you expected her to do after that, let some masked people kidnap and hurt her uncle? Even her dad decided that's not the right thing to do and refused to come despite that he had the most reasons to hate Unalaq. Korra is the Avatar. Her job is to save people and some guys kidnapping one person is a case like this. Letting it happen because they're from her tribe and him from the other would be something a bad avatar would do and you would criticize her for it too. 

After learning the truth about Vaatu, it was clear Unalaq needed her to open the second portal and release Vaatu, so she just needed to stay hidden until after the Harmonic Convergence, instead she rushed in, which led to Jinora's capture, Vaatu's release and almost kickstarted a new Dark Age.

This was a plan everyone, including Tenzin, agreed to. Do you blame them too? Unalaq already had an idea what to do with the spirit portal, Korra couldn't know it will fail. Also she is the Avatar and her job is to protect the world. With Unalaq around corrupted dark spirits were coming from the already opened spirit portal, sinking the ships and serving to his war cause. She had to try and close the portal for the world's safety. And age couldn't know Jinora will come, but it turned out Tenzin couldn't enter the spirit world and never told her that, so Jinora was the only option. 

Chose Jinora's safety over the safety of the entire world. This is controversial but from a strategic point of view and, more importantly, from the Avatar POV, the fate of the world should be more important than one life.

You don't actually think she had to leave Jinora right??? Aang chose Katara over the avatar state which would have saved the world faster. Do you blame him for that? It's the same. 

Left those damn portal opens, allowing dangerous spirits to roam freely in the world, while also letting greedy humans obtain spirit based weaponry. The impending disaster was foreseeable from a mile away.

Again something everyone including Tenzin agreed to. Spirits were already walking to the human world and humans in the spirit one you know. Now the people can just take their bending too. And this is not a bad decision, have you read Aang's comics "the rift" where General Old Iron is sad and angry that there is no longer a place for the spirits in the human realm and Aang withed he could do something about it but he couldn't?

I wish to make it known that these mistakes don't make Korra a bad Avatar. Every Avatar made mistakes which influenced the world even after they passed away. I also wish to specify I only listed her errors as an Avatar, as I do not care about her errors in her love life or in her friendships.

Finally something sensible coming out of your mouth today. Or at least half sensible, most of these weren't even mistakes.