What superhero starts with the letter y?

Answer 1

Yellowjacket AKA Giant-Man AKA Goliath AKA Ant-Man.

"After constant experimentation with size-changing via ingested capsules and particle-filled gas, Pym is eventually able to change size at will, and mentally generate Pym particles to change the sizes of other living beings or inanimate objects. Pym retains his normal strength when "ant" size, and possesses greatly increased strength and stamina when in "giant" form, courtesy of the increased mass. Pym's costume is synthetic stretch fabric composed of unstable molecules and automatically adapts to his shifting sizes.

The character also uses a cybernetic helmet for achieving rudimentary communication with ants and other higher order insects. As Yellowjacket, Pym wears artificial wings and has bio-blasters called "stingers" built into his gloves. Pym also carries a variety of weaponry, provisions, and scientific instruments, which are shrunken to the size of microchips and stored in the pockets of his uniform."