Each of the other future Avengers gets one in their initial appearance:
Spitfire's first use of her Firebird powers, defeating the MLP version of the Hulk.
Blueblood proving he really has changed, with his first act as Iron Pony being to save Rarity from Whiplash. Turns out this was a Secret Test of Character Rarity and Celestia set up for him, but he passed, so it counts.
Caramel's first act with the power of Captain Equestria being to hunt down the Loki spy who'd attempted to sabotage the project and capturing him. Especially impressive for a pony who up till then had a dismal track record of getting anything done right.
The Avengers managing to work together for their first real mission and defeat the Juggernaut.
Captain Equestria: Call me nopony then. Because I never give up. No matter what. Even if I know I'll just screw up again, I keep trying. Because every once in a while, I get a day like today. A day when I win.
The other fights are only slightly less impressive, as Firebird and Iron Pony manage to turn Iron Monger and the Red Skull's own Hannibal Lectures back on them before defeating them. Iron Pony even gives his own "World of Cardboard" Speech, though his somewhat lacks the "oomph" of the Captain's.
Iron Pony: (interrupting Red Skull's Hannibal Lecture about destiny) Stop. That's not greatness. That's just vanity. I got the two mixed up before. But let me tell you something. I never did anything. All I ever did was sit around lazily, devour food, complain, and treat everypony like dirt. That was my destiny. To be a burden until the day I died, and then forgotten by everypony save those who hated me. And had I clung to that stupid, selfish destiny, I'd be dead now. Pierced through the heart by a piece of masonry, my entire life bereft of meaning. [...] But I cast aside that destiny. I cast aside my idiotic 'superiority'. I got down on my knees and begged a pony I had once thought beneath me, not even worthy of my notice, to help me. And now? I'm here. [...] So I've decided. If destiny means being a selfish bully, blind to the needs of those around me... I want no part of it!
Big Mac's speech to Loki during their own fight, where he comes to terms with being both himself and Thor, rather than sharing a body, before defeating the God of Evil with ease including rather easily overcoming his I Surrender, Suckers moment and finishing him off with his own spell.
While he may be the Big Bad, Loki still has his moments. First, when he reveals how he's manipulated the entire story up to that point to his favor; then, when he shows that he anticipated Trixie's betrayal and deals with it; and finally, when he manages to die happy, content that his death will mutate all of Equestria, creating the world ruled by magic he'd always wanted.