(please log in to view the image) A furious Superboy Prime pounded on the barrier of reality. This assault caused ripples that altered reality, which was used as an explanation for character changes and retcons in DC continuity.
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(please log in to view the image) It was the punch that ended the first multiversal crisis, and it was so forceful a punch that the Green Lantern Corps, witnessing the punch from the other side of the antimatter universe, saw the Anti-Monitor's death flash and realized that it was all over.
1. Which was the more impressive feat/hardest punch?
2. Who (physical, non abstract) if anyone could survive either if these punches?
Hard to say which is more impressive but I can't think of any non-abstract beings that could survive those. I guess, in theory, Doomsday might've eventually been able to survive them after dying from the first one. I know that sounds crazy but with his regeneration and not being able to be killed with the same or lesser force of things that've killed him before after dying from one the first time he should be able to survive the next one.
__________________ Darwin's theory of evolution is the great white elephant of contemporary thought. It is large, completely useless, and the object of superstitious awe.-Dr. David Berlinski, Philosophy
Most people believe Evolution not because they themselves are dumb, but cause they trust the "experts" who are feeding them evolutionary fast food, and so they don't bother questioning whether or not it's true.
Kal-L's punch all the way. It was a glorious end to the greatest comic book crossover EVER, the first superhero ending the greatest threat the multiverse had ever seen.
"A furious Superboy Prime pounded on the barrier of reality. This assault..."
Are these your words, describing the event? Because, for me, "pounded" and "assault" imply more than one strike. In which case, I vote the second example -- where it seems to involve one punch -- as the greater feat, especially since one could contemplate a real-world comparison to the first example/punch(es), ie, black holes.
Black holes sort of "shatter" reality as we know it (one could say that SBP's punches were so fast that his fists - via relativistic effects - became extremely massive), but I don't know of any real-life phenomena which affects a whole multiverse (which, in thinking about this, strikes me as overdoing the one-upmanship nonsense).
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Shinier than a speeding bullet.