For me, writing that last chapter is the hardest of them all. I have to make sure all loose ends are tied up, and then, of course, there's the black moment and the HEA. Both have to be slam dunks. And I make it a bit worse on myself when I put the restraints on editing. As a matter of fact, during May Bootcamp, you couldn't go back and edit because the point was to complete a WIP in 30 days.
Back to the ending. That last pesky chapter and the characters are screaming at me to finish up already while I'm trying to ensure there's the big BANG! Yup, I'm frustrated with mine at the moment. I have the whole action climax set(my heroine is tied up and has passed out-the villain has turned on the gas. My hero is on his way to rescue her, of course, before the both of them are blown to smithereens) But, here's my problem. I need their black moment after this. Which I'm sure I'll get it sooner or later. I just prefer sooner!
How about you? Do you get frustrated with that last chapter or does it come fairly easy to you (Lucky you!)