It is not difficult to find words which contain a doubled RNL and no other RNLs:
On the other hand, words with tripled and quadrupled RNLs and no other RNLs are rare:
The following words have different pairings of adjacent doubled RNLs and no other RNLs.
Here, I search for solid words with as many of a particular RNL as possible but which contain no other RNLs.
Same doubled RNLs: CCAMPATUYOCC (Peru), CCARCCOLLACHAYOCC (a locality in Peru) has 3 x CC, an LL, and 7 Cs in total.
Different doubled RNLs: LLANFAREDD (Powys, Wales) VVALL (enter 1590 cit = wall)
The RNLs in these words appear in their correct alphabetical positions within each word.
The RNLs in each of these words appear in their correct alphabetical positions in relation to each other only.
The RNLs in these words are reverse local invariants.
SIX NOVEMDECILLION (ideal Roman window; 7 RNLs in an 11-letter window)
No other president's full name has Roman numeral letters (RNLs) that make a correctly-formed Roman numeral equal to the president's position in the list.
In general, the Roman widow contains each Roman numeral letter (RNL) at least once in any order.