Spoiler
the ending is in the trailer
Take Civil War for example. The Spider-Man reveal should've been kept to the big screen instead of the Superbowl trailer. Personally, I feel like it would've made a bigger impact that way and boosted the sales.
Another example I can think of is the most recent XXX movie. The whole Ice Cube reveal in the trailer essentially robbed the climax of any impact because you knew he was going to show up.l and save the day. Its a great action movie nonetheless, but just the fact that you know what was going to happen kills the momentum.
The worst offender of this that I can think of is Smurfs: The Lost Village where they show that, surprise, it's a village full of female Smurfs IN THE DAMN TRAILER!
Someone really needs to teach the media industry how to keep things a secret, because they're doing s terrible job at it.