maybe she dies if all 3 dragons die.

Phrasing

Never gonna happen. No normal human has a possibility of killing The Mountain. It has to be Arya. It's gonna take assassin voodoo mumbo jumbo to get close enough to him to kill him.
Even if it isn't Ayra, she is going to kill somebody/something that only she can because it can only be done with assassin voodoo. Nobody else can do it. Her entire story/journey is about this one killing she does that is crucial to the story's outcome.

Sesame Street: Respect is Coming

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I knew there was a reason why I liked you...

Maybe, but it can't be the end of Arya.
It just wouldn't be fitting.

https://www.digitalspy.com/tv/ustv/a...yas-kill-list/

I'd be fine if Arya didn't really do much more on the show. I think her killing all the Frey men was big enough. I really don't buy her character as some kind of super swords-woman, as shown during her sparring with Brienne.

If Sam can kill a white walker (that was more luck but still), the Hound can kill the Mountain. Audiences just love the David vs Goliath moments.

And The Mountain is no longer human. He's Frankenstein's monster/zombie. We still don't even know the extend of his un-dead powers. Smashing a few insolent townsfolk heads for disrespecting Cersei tells us nothing.

I'm assuming he can only be killed by cutting off his head or stabbing him in the eyes through the slits in his mask. In order to get close enough to him to do anything, you're close enough for him to get you, you've already lost. I suppose someone could throw a spear or knife from a distance and get him in the eye.
Ayra can get within striking distance by either doing fancy moves and getting past his defense, or wearing a Cersei mask.

Or one of those big ass dragons can burn him to a crisp.

I assume the Mountain will be the last line of defense in order to get to Cercei. I doubt that killing both would be a one man/girl job. Perhaps it's a Jaime/Hound/Arya group effort, unless it's that big ass dragon.

It's too personal for that. Would be a rip-off. If John Wick is chasing the guy who killed his dog would you be satisfied seeing him get hit by a car instead?

I would love it if the hound killed the mountain by pressing his eyes like the mountain did to the viper / prince...