Happy Birthday: Brainiac
Though not truly alive, Brainiac can date his creation to April 6, the day the Computer Tyrants of Colu created him. The green-skinned humanoid wreaked havoc across the galaxy, including shrinking several cities to subdue their populaces.
One of those cities was Kandor of Krypton. Years later, Brainiac encountered the man who would become his chief nemesis, Kal-el of Krypton—better known as Superman. It was a battle with Superman that forced Brainiac to destroy his original body and create a new, metallic skeleton form.
Brainiac has taken on several different forms since then, and his origin story has changed several times as well—sometimes he is an actual Coluan man instead of an android—but his twelfth-level intellect and his hatred for Superman continue unchanged to this day.