Created by Kaiser Cruger in an attempt to find a way to eliminate the Grimm as a whole, Exachrona is a mutant Grimm with the ability to adapt and become immune to whatever killed it. The motivations behind its creation are dubious and underhanded. The Atlas military tricked Kaiser into creating a bio weapon for eliminating the Grimm by using the collected info from Site-13 as a basis for the research. After months of experimentation, it was born. Small at first, Exachrona was subjected to various different ways of execution. Burning, electrocution, dismemberment and even being exposed to lethal doses of radiation, nothing worked. Every time he was “killed”, Exachrona would simple come back, immune to whatever killed him as well as growing bigger and becoming more powerful. Soon, it would begin to mutate even further, taking on a humanoid form. Fearing that he would become too powerful, Kaiser along with the others on the research team decided to put Exachrona in cryostasis until a permanent solution could be found. There he sleeps, slowly growing more powerful until he can break free and reign chaos and destruction upon Remnant.
Immunity to whatever “killed” him. Super speed (Capable of reaching speeds of mach 5). Firing beams of concentrated energy form his hands. Can rip through dimensions with nothing but brute strength.
Levels of Adaptability
Of course it's adaptation takes time which the severity of what initially "killed" it will effect how long it takes to come back. However, the stronger it becomes, the less time would be required for it to come back. For example, if it were to be decapitated, come back and have its head split open. It would take less time for the 2 halves of its head to heal and reform.
Most of Its abilities will be acquired with time and significant adaptation. So it will not start off with the dimension ripping and would require a significant amount of time to acquire that ability. No being, weapon or ability can kill it or stop it permanently, only hinder it for a finite amount of time.