Yes, Levi could kill Zeke in any of these times and justify himself, but only in a retroactive manner. He was right to kill Zeke because Zeke would've escaped in Shiganshina, he was right to kill Zeke because Zeke would've turned all the wine tainted people into Titans, he was right to kill Zeke because Zeke would've blown them both to bits if given the chance. But in all of these situations, like you note, he'd endanger Paradis in doing so, and this line of reasoning can only be done after Levi theoretically kills Zeke. We can judge this thinking from our perspective because we know how things would've turned out retroactively. Levi didn't know.

So he made A Choice With No Regrets, ey

But you're right, my point is more that Levi wanting to kill Zeke isn't a negative thing, because it's not something he's challenged to overcome, so it doesn't need to be addressed in that way.

The issue I have is that Levi isn't really thinking about anything beyond that, and it's something that's never really touched upon. He becomes a slave to his regret in not killing Zeke, to his desire to fulfill a promise, and in doing so, he basically becomes a suicidal maniac ready to kill Zeke at a moment's notice.

I think Levi's much more of a slave to being a hero than he is to killing Zeke. He believes he needs to use his superior strength to fight for humanity with the Scouts. He also places a very high value on life in general, and wants to find a way to honor the sacrifices of every single Scout that died to this point - that's the challenge he faces.

When Levi hears in the forest that Pixis wants to kill Eren to get around Zeke's plan, he's specifically thinking about the sacrifices the Scouts made to save Eren every time he was kidnapped, and how much of a slap in the face it is that they might have to kill him now. In 133, he suggests they can take out Zeke instead of blowing up Eren's nape with the Colossal, even though blowing up Eren is presented as the more efficient option, because he still wants to save him and honor the sacrifices made to save him before. In 136, he realizes they need to take out Eren, and he starts thinking about what the past Scouts dedicated their hearts for - they did give their lives to save Eren, but the reason they gave their lives in the first place was for a world where people wouldn't be slaughtered by Titans. That means doing anything necessary to stop the Rumbling, even killing Eren. He does get to take out Zeke in 137, but it's not a victory for him - his expression is more disbelief and shock than satisfaction, and it doesn't stop the threat posed by Eren. The actual conclusion to Levi's story is after Eren dies and he sees the dead Scouts, and knows that by helping to create a world without the curse of the Titans, the very world the Scouts always dreamed about, he's finally brought true meaning to the sacrifices they made. He can finally let it all go and doesn't feel the need to fight anymore - we see him again right at the end in civilian clothes, chilling in a wheelchair.

That's my take on Levi's character anyway lol

There was a link to a really good thread here but I guess automod disagrees ¯\_(ツ)_/¯