Eternity was unable to defeat The Time Eater for being extremely strong for her. She then asks for Franklin Richards to deal with him before he destroys Booth Space and Time.
The battle happens at The Hearth of The Universe.
The Time Eater
The Time Eater possesses a vast mastery and control over the manipulation of time and space itself. Its time-space manipulation was in fact so advanced that it was able to interfere with alternate timelines such as Crisis City, which is supposed to be removed from the original timeline. Its primary and only known power in its original form, is its ability to erase time and space, which allows the Time Eater to erase events and place from history, as if they never happened. It is unknown what other powers the Time Eater had in its original form.
Besides supernatural powers and weapons, the Time Eater also possesses immense amounts of physical strength. Even in its incomplete form, it was able to easily knock Sonic into unconsciousness with a single swing of its arm. After being completed, the Time Eater was able to effortlessly repel both Classic and Modern Sonic's attacks and knock them out with brute force alone (Eggman even admitted he was holding back the Time Eater's strength) and during the final battle it proved it was able to briefly knock back and immobilize both Classic and Modern Super Sonic when catching them it its grip.
-Morals on and bloodlust off.