Capital letters that have right angles depend on the font, but I can find 10:
2 Lower case letters with right angles are:
the alphabet has 26 letters in it
there are 33 letters in the cambodian alphabet
There are 26 letters in the English version of the Latin alphabet.
There are 52 letters in Sanskrit language.
There are exactly 42 Incan letters.
There are 26 letters in the alphabet.
the alphabet has 26 letters in it
The official Philippine alphabet has 28 letters.
The English language alphabet has 26 letters.
There were 22 letters in the Phoenician alphabet.
There are 28 letters in the Arabic alphabet.
The Somali Latin alphabet has 32 letters. The Somali Osmanya alphabet has 22 letters.
26 in our alphabet.
There are 24 letters in the Greek Alphabet
there are 24 letters in the Elizabethan alphabet.
there are 33 letters in the cambodian alphabet
There are 28 letters in the Arabic alphabet.