Spoiler Like Joe Joe said, the moves Coin made were highly suspicious of being a tyrant. After Katniss recovers, she confronts Snow in the greenhouse who makes her suspect Coin. Then when she talks to Gale, Gale can't deny the bombing was similar to a plan he worked on with Coin. Coin also suggests a new Hunger Games for the kids of families loyal to the old regime. The black oil receding was maybe to allow the Peacemakers to go into the courtyard to clean up the threats, but it would've made more sense for the Capitol to merely bomb the courtyard with an air strike. The oil had raised to the level of the cameras so they weren't functional when Katniss's group moved. Those gollums seemed very random and plot element-like. They should've been featured in a previous movie. I didn't really care when any of Team Katniss died as everyone in the team was pretty much fodder.
Spoiler Yeah, I got that there was clearly evidence that Coin was putting herself in a position to be a tyrant just like Snow. But honestly there was no direct evidence that she was the one that ordered the bombing that killed Primrose and she put forth an idea of doing the symbolic hunger games, but then put it to a vote. So while there are certainly reasons to SUSPECT she was pulling a Snow, I didn't feel like there was any where near enough evidence to just shoot her in cold blood. That was a very un-Catniss like moment, from what I got of her character in these 4 movies. Just my opinion. I didn't think about the cameras getting oiled over.
Spoiler From what I remember, the book made it seem like killing Coin was almost entirely sure to her positioning herself to be like Snow. Continuing the Hunger Games, taking power, etc. I think the movie emphasized Prim's death as a motivation more than the book did.
What an underwhelming way to end a series. They fix none of the issues from the book and make changes that weren't necessary. And the whole film had a slow, methodical, emotionless pace to it. I still enjoyed it but nowhere near as much as the others. They might have been better off making one long movie instead of splitting it into two.
