PH
Mew began by unleashing the power of its ability, "Transcendent Psionic Energy Conversion Field" - creating a field of energy that converted all mental energy into raw power. Jirachi responded with its ability, "Eldritch Reality Shattering Shield" - a shield that protected Jirachi from all reality-warping attacks.
Mew then attacked with its move, "Cosmic Singularity Collapse" - a blast of energy that compressed space itself into a singularity. Jirachi countered with "Heavenly Nexus Disintegration Beam" - a beam that disintegrated anything it touched.
The battle raged on, with Mew using "Quantum Thaumaturgy" to manipulate matter and energy at will, and Jirachi using "Omnipotent Reality Manipulation" to control all aspects of reality.
Finally, Mew unleashed its ultimate move, "Reality Distortion Bombardment" - a barrage of attacks that distorted reality on a massive scale. But Jirachi was ready and used its ultimate move, "Cosmic Omnipotence Release" - a blast of energy that granted Jirachi true omnipotence.
In the end, Jirachi emerged victorious, its ultimate move proving too much for Mew to handle. The winner of the battle was Jirachi.