No one liking this, no?

It's pretty good. I like the style you went for. I'd say the way the dragon's shattered kind of reminds me of MK Annihilation, but I feel like some might take that as an insult. I think you could probably come up with a better tagline though. Nothing wrong with yours, but picture something witty but still relevant. Think of Deadpool's movie using "With great power comes great irresponsibility".

The movie is of a serious tone. It'll have a more serious tone than the original for sure, so having a "witty" tagline wouldn't fit.

Since it's Earth's last defense, it is their final chance. So it kind of fits. Plus I used this tagline years ago on another one of my very old picture edits (on my Deviant Art page).