Darren Cross is a fictional character from the Marvel Comics universe, primarily known as the antagonist Yellowjacket. He is a brilliant scientist and former colleague of Hank Pym, the original Ant-Man. Cross is often portrayed as ambitious and ruthless, seeking to harness the power of the Pym Particles for his own gain. In various storylines, Cross's obsession with technology and power leads him to create advanced suits and weapons, allowing him to shrink in size while maintaining strength. His character often embodies themes of ambition and the ethical dilemmas of scientific advancement, making him a complex villain in the Marvel narrative.