Diagonal Alphabet

Charcoal, 2 bytes

↘β

Try it online!

How?

 β - the lowercase alphabet
↘  - direction

Exactly the kind of challenge for which Charcoal was originally designed.

C, 45 bytes

f(i){for(i=0;++i<27;)printf("%*c\n",i,i+96);}

Thanks to @Dennis for saving 5 bytes!

05AB1E, 14 8 6 bytes

-2 bytes thanks to @Emigna

AvyNú»

How it works

A      # lowercase alphabet
 v     # for letter in alphabet
  y    # push letter
   N   # push index of letter
    ú  # Pad letter with index of letter spaces
     » # Join with stack on newline.

Try it online!

Original version, 14 bytes

26FNð×N65+ç«}»