Dark humor makes sense but is dark:
"I'm the second worst thing to happen to these orphans"
Shock humor is something that doesn't necessarily make sense:
"I can't see the horizon- HATSUNE MIKU?!"
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Anonymous#16w
They overlap often. A good example of dark shock humor is 9/11 jokes, where a normal video/situation unexpectedly switches to referencing 9/11
(Often made by Jschlatt viewers for some reason)