After reaching his limit of Entropy, his body couldn't heal, and it didn't matter if he had an infinite lifespan. So it was the same thing he did to Martial Will and the others. The only difference was that it had happened to him with one attack, whereas he spent a lot of time grinding Martial Will and the others to their limit.
The only good news was that the Devouring Supreme Metac had detached from his existence and successfully entered the River of Time. Unfortunately, the attack wasn't over.
Apparently, Loki's existence wasn't big enough to contain the power of that attack. So the rest of the power of the attack spilled into the River of Time, looking for him.
The force of destruction entered the River of Time as a black, surging river. The black river latched onto every string in the River of Time that contained images of Loki and surged into them, killing the Loki in them.
