Well He That Remains came by just to show that everything we experience is always part of a bigger loop. You can fucking kill him and even slam the break; crash to his design of the the highest number of alternate dimensions and then some and it won't stop the loop. 99.99% of the time he'll be back. We only need to consciously accept the concept of no more than the notion to summon his return. Even if we were to successfully crack the time management mech and undo his manipulation, he'll be back when we track him down to build another one.
The Loop is more nature than matter to energy combined. When everything in all of reality would expand infinitely far apart, the whole shebang goes lateral mirror again with a whole new dimension. There is no end to any aspect of reality. Anywhere it would be, turns out it's "just" "another" Loop Mirror.