The Original Creator is not a monster, he is a "Universal Magnet". When he closed his eyes, everything in the universe began to attract him. This is called the "Law of Convergence".
Amon: He realized that everything he had 'stole' was not his own. The Original Creator sucked up Amon's monocle and parasites. Amon didn't even get a chance to scream, he turned into a dust of logic.
Einstein and Saitama: Einstein's watch shattered because there was no such thing as "time" or "space" left. Saitama tried to clench his fists, but found his body merging into waves of light. To the Original Creator, 'energy' or 'physical laws' had no meaning.
Klein Moretti: Klein made a last-ditch effort to survive with his 'Sefirah Castle'. But the Original Creator only sighed. Klein realized that what he thought was 'Godhood' was actually just a dream seen by the Original Creator in his sleep.