There is nothing to be found behind the TLD as the DNS request will only contain the domain itself (no paths, etc.). Hence, @devnull's regex is identical to
\.(me|com|de)$
for Pi-hole.
Note that the point . is the wildcard character in the regex language. For matching a true dot, you need to write \. Please see Redirecting... for further details.
Of course, forgot that while testing.
But should/could that work in combination with a blocklist?
As mentioned I'd like to write these in a blocklist and not in the local blacklist of pi-hole.