Username data for naturally taken usernames (not counting username changes):

Last:

X: ?

XX: @66

2num: @98

2char/letter: @dt (maybe)

3char/letter: ? (Maybe @/ao3, not @‘ing cause unsure)

bX: @bz

cX: @cz

Second lasts:

X: ?

XX: @33 (@/55 had a username change and is now @-_ ).

2num: unsure, possibly @97

2char/letter: maybe @ds

3char/letter: ?

bX: @bx (lol)

cX: @cx (lol)

Data from: me, @up, the api and random posts