The MCU is yet to pay off a major Pym Particle tease set up in 2015's Ant-Man. Despite starting out as a low-level burglar, Scott Lang has risen to become one of the Avengers' most important members, having the key to time travel in Avengers: Endgame and meeting Kang the Conqueror before anyone else in Ant-Man and the Wasp: Quantumania. In his first MCU appearance, however, Scott Lang faced more grounded threats such as Darren Cross and, secretly, Hydra.
https://screenrant.com/ant-man-hydra-pym-particles-cliffhanger/