Backwards Alphabet Triangle
Haskell, 53 bytes



[tail$do c&lt;-reverse a;' ':[c|c&lt;=d]|d&lt;-a]
a=['A'..'Z']


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This uses that each line has exactly 25 spaces. So, instead of separately handling the prefix spaces and the spaces between letters, we take 26 spaces, and decide whether to put a letter after each. This unfortunately gives one extra leading space, which we remove.



54 bytes



foldl(\m c-&gt;map(' ':)m++[c:' ':last m])["A"]['B'..'Z']


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55 bytes



"A"%['B'..'[']
s%(h:t)=((' '&lt;$t)++s):(h:' ':s)%t
s%_=[]


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