Darkseid (real name: Uxas) is one of the main antagonists in the Superman comics and other DC media. He is a merciless tyrant and a member of an extraterrestrial race of deities known as New Gods. He was widely regarded as one of the DC universe's most powerful and malevolent villains of all time.
Darkseid is also the inspiration for Thanos of Marvel comics, as stated several times by Thanos original creators.