4. Peter Parker (Spider-Man)

Gifted high-school student Peter Parker had barely ever stepped outside of Queens before being recruited by Tony Stark to help stop Captain America and his allies from protecting wanted fugitive Bucky Barnes. And with that, Parker, and his surrogate son-style relationship with Tony, became the beating heart of the MCU's Phase 3. As a child "thwipping" about in the deadly affairs of grown-ups (and Mad Titans), young Parker has defeated Vulture, Shocker, disgruntled Stark Industries technician Mysterio, and his own fears about asking MJ out on a date. But it was Parker's death during The Snap that hit Tony the hardest, and eventually convinced the Armored Avenger to join the others in a "time heist" to retrieve the Stones. Parker's wide-eyed optimism and eagerness to do good was exactly what the MCU needed, and exactly what the Avengers needed to undo all of Thanos' damage.

Most recently, Peter was reminded of the great power/great responsibility motto that is core to his character as he lost his Aunt May and gave up all of his friends for the betterment of those around him.