The loss proved that the team is not 'invincible'.
an 'invincible' army
(..) It's mine! - What should we do with it? - We? Just saying, that's the Elder Wand. The most powerful wand in the world. With that, he'd be invincible. Together. - Bag? - Yeah. Jumper? I'm gonna miss you. (..)2011 Harry Potter and the Deathly Hallows: Part 2