This is true, and now that I just read that (after writing the above) that's annoying me. But until you pointed it out I was okay with it. So I'm sure I'll get over it.
Yup, I'm over it now. Because I realized it does have an ending. The final fight scene is not about the fight, the action is incidental. It's all about their relationship, and in that fight they fight as one. For the first time, their relationship is solid. That is the ending.
The spy stuff in this movie is all unimportant, but cool, window dressing.
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