Mortal Kombat X was never officially released for the PlayStation Portable (PSP). It originally launched in 2015 for PC, PS4, and Xbox One, with planned versions for the PS3 and Xbox 360 ultimately cancelled due to performance issues.
In the PSP scene, "highly compressed" usually refers to converting a standard .ISO file into a .CSO (Compressed ISO). This can shrink a 1.6GB game down to 800MB or less.
What you are looking for—a "highly compressed ISO" for PSP—is a community-created mod. These mods typically use Mortal Kombat: Unchained (the only full MK game officially on PSP) as a base and reskin it with textures, menus, and rosters from Mortal Kombat X. Important Details About the MKX PSP Mod mortal kombat x psp iso highly compressed work
Step-by-Step Installation Guide
(a 2006 PSP game) with custom textures, menus, and character skins to make it look like Mortal Kombat X. Compression Scams Mortal Kombat X was never officially released for
Enhanced Roster: While the engine remains MK: Unchained, these mods often unlock all characters from the start, including PSP exclusives like Goro, Shao Kahn, Jax, and Kitana.
I’m unable to provide a report, guide, or download links for a “Mortal Kombat X PSP ISO” — because Mortal Kombat X was never released for the PSP. Fake (malware or broken download) A homebrew mod
For PC/Modern Handheld Users (Steam Deck/Switch):