The answer is "No".
Everyone is always under the impression that in superhero stories, the heroes always win. But it isn't the case always. There will be loss in some form or the other. It could be destruction of their safehouse/base, the loss of a powerful artifact, or the death of a hero.
Oftentimes, even when the good guys win it feels like they've lost – and if you’ve seen Avengers: Endgame, you’ll know what we mean. While this might be rare in the movies, the Avengers have seen far more ups and downs in the comics. Here are five times the Avengers lost...
There are several incidences in the past way before the end game when the avengers were in dispute with the Scarlet Witch who blamed them for the disappearance of her children.
There was another time when Norman Osborn takes over SHIELD and removes all avengers from the team making the out casts and re-branding them with villains.
The Onslaught crossover between X men and Avengers where the avengers had to escape into an alternate universe instead of fighting and winning is by far their biggest failure.
Although it seems like a common notion for the heroes to win all the time, it's important have a little bit of emotional reality with the same.